Ubuntu Manpage: drbdsetup - Configure the DRBD kernel module

Provided by: drbd-utils_9.15.0-1ubuntu0.1_amd64

NAME

       drbdsetup - Configure the DRBD kernel module

SYNOPSIS

       drbdsetup command {argument...} [option...]

DESCRIPTION

       The drbdsetup utility serves to configure the DRBD kernel module and to show its current
       configuration. Users usually interact with the drbdadm utility, which provides a more
       high-level interface to DRBD than drbdsetup. (See drbdadm's --dry-run option to see how
       drbdadm uses drbdsetup.)

       Some option arguments have a default scale which applies when a plain number is specified
       (for example Kilo, or 1024 times the numeric value). Such default scales can be overridden
       by using a suffix (for example, M for Mega). The common suffixes K = 2^10 = 1024, M = 1024
       K, and G = 1024 M are supported.

COMMANDS

drbdsetup attach minor lower_dev meta_data_dev meta_data_index,
drbdsetup disk-options minor
The attach command attaches a lower-level device to an existing replicated device. The
disk-options command changes the disk options of an attached lower-level device. In
either case, the replicated device must have been created with drbdsetup new-minor.

Both commands refer to the replicated device by its minor number. lower_dev is the
name of the lower-level device. meta_data_dev is the name of the device containing
the metadata, and may be the same as lower_dev. meta_data_index is either a numeric
metadata index, or the keyword internal for internal metadata, or the keyword flexible
for variable-size external metadata. Available options:

--al-extents extents
DRBD automatically maintains a "hot" or "active" disk area likely to be written to
again soon based on the recent write activity. The "active" disk area can be
written to immediately, while "inactive" disk areas must be "activated" first,
which requires a meta-data write. We also refer to this active disk area as the
"activity log".

The activity log saves meta-data writes, but the whole log must be resynced upon
recovery of a failed node. The size of the activity log is a major factor of how
long a resync will take and how fast a replicated disk will become consistent
after a crash.

The activity log consists of a number of 4-Megabyte segments; the al-extents
parameter determines how many of those segments can be active at the same time.
The default value for al-extents is 1237, with a minimum of 7 and a maximum of
65536.

Note that the effective maximum may be smaller, depending on how you created the
device meta data, see also drbdmeta(8) The effective maximum is 919 * (available
on-disk activity-log ring-buffer area/4kB -1), the default 32kB ring-buffer
effects a maximum of 6433 (covers more than 25 GiB of data) We recommend to keep
this well within the amount your backend storage and replication link are able to
resync inside of about 5 minutes.

--al-updates {yes | no}
With this parameter, the activity log can be turned off entirely (see the
al-extents parameter). This will speed up writes because fewer meta-data writes
will be necessary, but the entire device needs to be resynchronized opon recovery
of a failed primary node. The default value for al-updates is yes.

--disk-barrier,
--disk-flushes,
--disk-drain
DRBD has three methods of handling the ordering of dependent write requests:

disk-barrier
Use disk barriers to make sure that requests are written to disk in the right
order. Barriers ensure that all requests submitted before a barrier make it to
the disk before any requests submitted after the barrier. This is implemented
using 'tagged command queuing' on SCSI devices and 'native command queuing' on
SATA devices. Only some devices and device stacks support this method. The
device mapper (LVM) only supports barriers in some configurations.

Note that on systems which do not support disk barriers, enabling this option
can lead to data loss or corruption. Until DRBD 8.4.1, disk-barrier was turned
on if the I/O stack below DRBD did support barriers. Kernels since
linux-2.6.36 (or 2.6.32 RHEL6) no longer allow to detect if barriers are
supported. Since drbd-8.4.2, this option is off by default and needs to be
enabled explicitly.

disk-flushes
Use disk flushes between dependent write requests, also referred to as 'force
unit access' by drive vendors. This forces all data to disk. This option is
enabled by default.

disk-drain
Wait for the request queue to "drain" (that is, wait for the requests to
finish) before submitting a dependent write request. This method requires that
requests are stable on disk when they finish. Before DRBD 8.0.9, this was the
only method implemented. This option is enabled by default. Do not disable in
production environments.

From these three methods, drbd will use the first that is enabled and supported by
the backing storage device. If all three of these options are turned off, DRBD
will submit write requests without bothering about dependencies. Depending on the
I/O stack, write requests can be reordered, and they can be submitted in a
different order on different cluster nodes. This can result in data loss or
corruption. Therefore, turning off all three methods of controlling write ordering
is strongly discouraged.

A general guideline for configuring write ordering is to use disk barriers or disk
flushes when using ordinary disks (or an ordinary disk array) with a volatile
write cache. On storage without cache or with a battery backed write cache, disk
draining can be a reasonable choice.

--disk-timeout
If the lower-level device on which a DRBD device stores its data does not finish
an I/O request within the defined disk-timeout, DRBD treats this as a failure. The
lower-level device is detached, and the device's disk state advances to Diskless.
If DRBD is connected to one or more peers, the failed request is passed on to one
of them.

This option is dangerous and may lead to kernel panic!

"Aborting" requests, or force-detaching the disk, is intended for completely
blocked/hung local backing devices which do no longer complete requests at all,
not even do error completions. In this situation, usually a hard-reset and
failover is the only way out.

By "aborting", basically faking a local error-completion, we allow for a more
graceful swichover by cleanly migrating services. Still the affected node has to
be rebooted "soon".

By completing these requests, we allow the upper layers to re-use the associated
data pages.

If later the local backing device "recovers", and now DMAs some data from disk
into the original request pages, in the best case it will just put random data
into unused pages; but typically it will corrupt meanwhile completely unrelated
data, causing all sorts of damage.

Which means delayed successful completion, especially for READ requests, is a
reason to panic(). We assume that a delayed *error* completion is OK, though we
still will complain noisily about it.

The default value of disk-timeout is 0, which stands for an infinite timeout.
Timeouts are specified in units of 0.1 seconds. This option is available since
DRBD 8.3.12.

--md-flushes
Enable disk flushes and disk barriers on the meta-data device. This option is
enabled by default. See the disk-flushes parameter.

--on-io-error handler
Configure how DRBD reacts to I/O errors on a lower-level device. The following
policies are defined:

pass_on
Change the disk status to Inconsistent, mark the failed block as inconsistent
in the bitmap, and retry the I/O operation on a remote cluster node.

call-local-io-error
Call the local-io-error handler (see the handlers section).

detach
Detach the lower-level device and continue in diskless mode.

--read-balancing policy
Distribute read requests among cluster nodes as defined by policy. The supported
policies are prefer-local (the default), prefer-remote, round-robin,
least-pending, when-congested-remote, 32K-striping, 64K-striping, 128K-striping,
256K-striping, 512K-striping and 1M-striping.

This option is available since DRBD 8.4.1.

resync-after minor
Define that a device should only resynchronize after the specified other device.
By default, no order between devices is defined, and all devices will
resynchronize in parallel. Depending on the configuration of the lower-level
devices, and the available network and disk bandwidth, this can slow down the
overall resync process. This option can be used to form a chain or tree of
dependencies among devices.

--size size
Specify the size of the lower-level device explicitly instead of determining it
automatically. The device size must be determined once and is remembered for the
lifetime of the device. In order to determine it automatically, all the
lower-level devices on all nodes must be attached, and all nodes must be
connected. If the size is specified explicitly, this is not necessary. The size
value is assumed to be in units of sectors (512 bytes) by default.

--discard-zeroes-if-aligned {yes | no}
There are several aspects to discard/trim/unmap support on linux block devices.
Even if discard is supported in general, it may fail silently, or may partially
ignore discard requests. Devices also announce whether reading from unmapped
blocks returns defined data (usually zeroes), or undefined data (possibly old
data, possibly garbage).

If on different nodes, DRBD is backed by devices with differing discard
characteristics, discards may lead to data divergence (old data or garbage left
over on one backend, zeroes due to unmapped areas on the other backend). Online
verify would now potentially report tons of spurious differences. While probably
harmless for most use cases (fstrim on a file system), DRBD cannot have that.

To play safe, we have to disable discard support, if our local backend (on a
Primary) does not support "discard_zeroes_data=true". We also have to translate
discards to explicit zero-out on the receiving side, unless the receiving side
(Secondary) supports "discard_zeroes_data=true", thereby allocating areas what
were supposed to be unmapped.

There are some devices (notably the LVM/DM thin provisioning) that are capable of
discard, but announce discard_zeroes_data=false. In the case of DM-thin, discards
aligned to the chunk size will be unmapped, and reading from unmapped sectors will
return zeroes. However, unaligned partial head or tail areas of discard requests
will be silently ignored.

If we now add a helper to explicitly zero-out these unaligned partial areas, while
passing on the discard of the aligned full chunks, we effectively achieve
discard_zeroes_data=true on such devices.

Setting discard-zeroes-if-aligned to yes will allow DRBD to use discards, and to
announce discard_zeroes_data=true, even on backends that announce
discard_zeroes_data=false.

Setting discard-zeroes-if-aligned to no will cause DRBD to always fall-back to
zero-out on the receiving side, and to not even announce discard capabilities on
the Primary, if the respective backend announces discard_zeroes_data=false.

We used to ignore the discard_zeroes_data setting completely. To not break
established and expected behaviour, and suddenly cause fstrim on thin-provisioned
LVs to run out-of-space instead of freeing up space, the default value is yes.

This option is available since 8.4.7.

--rs-discard-granularity byte
When rs-discard-granularity is set to a non zero, positive value then DRBD tries
to do a resync operation in requests of this size. In case such a block contains
only zero bytes on the sync source node, the sync target node will issue a
discard/trim/unmap command for the area.

The value is constrained by the discard granularity of the backing block device.
In case rs-discard-granularity is not a multiplier of the discard granularity of
the backing block device DRBD rounds it up. The feature only gets active if the
backing block device reads back zeroes after a discard command.

The default value of is 0. This option is available since 8.4.7.

drbdsetup peer-device-options resource peer_node_id volume
These are options that affect the peer's device.

--c-delay-target delay_target,
--c-fill-target fill_target,
--c-max-rate max_rate,
--c-plan-ahead plan_time
Dynamically control the resync speed. This mechanism is enabled by setting the
c-plan-ahead parameter to a positive value. The goal is to either fill the buffers
along the data path with a defined amount of data if c-fill-target is defined, or
to have a defined delay along the path if c-delay-target is defined. The maximum
bandwidth is limited by the c-max-rate parameter.

The c-plan-ahead parameter defines how fast drbd adapts to changes in the resync
speed. It should be set to five times the network round-trip time or more. Common
values for c-fill-target for "normal" data paths range from 4K to 100K. If
drbd-proxy is used, it is advised to use c-delay-target instead of c-fill-target.
The c-delay-target parameter is used if the c-fill-target parameter is undefined
or set to 0. The c-delay-target parameter should be set to five times the network
round-trip time or more. The c-max-rate option should be set to either the
bandwidth available between the DRBD-hosts and the machines hosting DRBD-proxy, or
to the available disk bandwidth.

The default values of these parameters are: c-plan-ahead = 20 (in units of 0.1
seconds), c-fill-target = 0 (in units of sectors), c-delay-target = 1 (in units of
0.1 seconds), and c-max-rate = 102400 (in units of KiB/s).

Dynamic resync speed control is available since DRBD 8.3.9.

--c-min-rate min_rate
A node which is primary and sync-source has to schedule application I/O requests
and resync I/O requests. The c-min-rate parameter limits how much bandwidth is
available for resync I/O; the remaining bandwidth is used for application I/O.

A c-min-rate value of 0 means that there is no limit on the resync I/O bandwidth.
This can slow down application I/O significantly. Use a value of 1 (1 KiB/s) for
the lowest possible resync rate.

The default value of c-min-rate is 250, in units of KiB/s.

--resync-rate rate
Define how much bandwidth DRBD may use for resynchronizing. DRBD allows "normal"
application I/O even during a resync. If the resync takes up too much bandwidth,
application I/O can become very slow. This parameter allows to avoid that. Please
note this is option only works when the dynamic resync controller is disabled.

drbdsetup check-resize minor
Remember the current size of the lower-level device of the specified replicated
device. Used by drbdadm. The size information is stored in file
/var/lib/drbd/drbd-minor-minor.lkbd.

drbdsetup new-peer resource peer_node_id,
drbdsetup net-options resource peer_node_id
The new-peer command creates a connection within a resource. The resource must have
been created with drbdsetup new-resource. The net-options command changes the network
options of an existing connection. Before a connection can be activated with the
connect command, at least one path need to added with the new-path command. Available
options:

--after-sb-0pri policy
Define how to react if a split-brain scenario is detected and none of the two
nodes is in primary role. (We detect split-brain scenarios when two nodes connect;
split-brain decisions are always between two nodes.) The defined policies are:

disconnect
No automatic resynchronization; simply disconnect.

discard-younger-primary,
discard-older-primary
Resynchronize from the node which became primary first
(discard-younger-primary) or last (discard-older-primary). If both nodes
became primary independently, the discard-least-changes policy is used.

discard-zero-changes
If only one of the nodes wrote data since the split brain situation was
detected, resynchronize from this node to the other. If both nodes wrote data,
disconnect.

discard-least-changes
Resynchronize from the node with more modified blocks.

discard-node-nodename
Always resynchronize to the named node.

--after-sb-1pri policy
Define how to react if a split-brain scenario is detected, with one node in
primary role and one node in secondary role. (We detect split-brain scenarios when
two nodes connect, so split-brain decisions are always among two nodes.) The
defined policies are:

disconnect
No automatic resynchronization, simply disconnect.

consensus
Discard the data on the secondary node if the after-sb-0pri algorithm would
also discard the data on the secondary node. Otherwise, disconnect.

violently-as0p
Always take the decision of the after-sb-0pri algorithm, even if it causes an
erratic change of the primary's view of the data. This is only useful if a
single-node file system (i.e., not OCFS2 or GFS) with the allow-two-primaries
flag is used. This option can cause the primary node to crash, and should not
be used.

discard-secondary
Discard the data on the secondary node.

call-pri-lost-after-sb
Always take the decision of the after-sb-0pri algorithm. If the decision is to
discard the data on the primary node, call the pri-lost-after-sb handler on
the primary node.

--after-sb-2pri policy
Define how to react if a split-brain scenario is detected and both nodes are in
primary role. (We detect split-brain scenarios when two nodes connect, so
split-brain decisions are always among two nodes.) The defined policies are:

disconnect
No automatic resynchronization, simply disconnect.

violently-as0p
See the violently-as0p policy for after-sb-1pri.

call-pri-lost-after-sb
Call the pri-lost-after-sb helper program on one of the machines unless that
machine can demote to secondary. The helper program is expected to reboot the
machine, which brings the node into a secondary role. Which machine runs the
helper program is determined by the after-sb-0pri strategy.

--allow-two-primaries
The most common way to configure DRBD devices is to allow only one node to be
primary (and thus writable) at a time.

In some scenarios it is preferable to allow two nodes to be primary at once; a
mechanism outside of DRBD then must make sure that writes to the shared,
replicated device happen in a coordinated way. This can be done with a
shared-storage cluster file system like OCFS2 and GFS, or with virtual machine
images and a virtual machine manager that can migrate virtual machines between
physical machines.

The allow-two-primaries parameter tells DRBD to allow two nodes to be primary at
the same time. Never enable this option when using a non-distributed file system;
otherwise, data corruption and node crashes will result!

--always-asbp
Normally the automatic after-split-brain policies are only used if current states
of the UUIDs do not indicate the presence of a third node.

With this option you request that the automatic after-split-brain policies are
used as long as the data sets of the nodes are somehow related. This might cause a
full sync, if the UUIDs indicate the presence of a third node. (Or double faults
led to strange UUID sets.)

--connect-int time
As soon as a connection between two nodes is configured with drbdsetup connect,
DRBD immediately tries to establish the connection. If this fails, DRBD waits for
connect-int seconds and then repeats. The default value of connect-int is 10
seconds.

--cram-hmac-alg hash-algorithm
Configure the hash-based message authentication code (HMAC) or secure hash
algorithm to use for peer authentication. The kernel supports a number of
different algorithms, some of which may be loadable as kernel modules. See the
shash algorithms listed in /proc/crypto. By default, cram-hmac-alg is unset. Peer
authentication also requires a shared-secret to be configured.

--csums-alg hash-algorithm
Normally, when two nodes resynchronize, the sync target requests a piece of
out-of-sync data from the sync source, and the sync source sends the data. With
many usage patterns, a significant number of those blocks will actually be
identical.

When a csums-alg algorithm is specified, when requesting a piece of out-of-sync
data, the sync target also sends along a hash of the data it currently has. The
sync source compares this hash with its own version of the data. It sends the sync
target the new data if the hashes differ, and tells it that the data are the same
otherwise. This reduces the network bandwidth required, at the cost of higher cpu
utilization and possibly increased I/O on the sync target.

The csums-alg can be set to one of the secure hash algorithms supported by the
kernel; see the shash algorithms listed in /proc/crypto. By default, csums-alg is
unset.

--csums-after-crash-only
Enabling this option (and csums-alg, above) makes it possible to use the checksum
based resync only for the first resync after primary crash, but not for later
"network hickups".

In most cases, block that are marked as need-to-be-resynced are in fact changed,
so calculating checksums, and both reading and writing the blocks on the resync
target is all effective overhead.

The advantage of checksum based resync is mostly after primary crash recovery,
where the recovery marked larger areas (those covered by the activity log) as
need-to-be-resynced, just in case. Introduced in 8.4.5.

--data-integrity-alg alg
DRBD normally relies on the data integrity checks built into the TCP/IP protocol,
but if a data integrity algorithm is configured, it will additionally use this
algorithm to make sure that the data received over the network match what the
sender has sent. If a data integrity error is detected, DRBD will close the
network connection and reconnect, which will trigger a resync.

The data-integrity-alg can be set to one of the secure hash algorithms supported
by the kernel; see the shash algorithms listed in /proc/crypto. By default, this
mechanism is turned off.

Because of the CPU overhead involved, we recommend not to use this option in
production environments. Also see the notes on data integrity below.

--fencing fencing_policy
Fencing is a preventive measure to avoid situations where both nodes are primary
and disconnected. This is also known as a split-brain situation. DRBD supports the
following fencing policies:

dont-care
No fencing actions are taken. This is the default policy.

resource-only
If a node becomes a disconnected primary, it tries to fence the peer. This is
done by calling the fence-peer handler. The handler is supposed to reach the
peer over an alternative communication path and call 'drbdadm outdate minor'
there.

resource-and-stonith
If a node becomes a disconnected primary, it freezes all its IO operations and
calls its fence-peer handler. The fence-peer handler is supposed to reach the
peer over an alternative communication path and call 'drbdadm outdate minor'
there. In case it cannot do that, it should stonith the peer. IO is resumed as
soon as the situation is resolved. In case the fence-peer handler fails, I/O
can be resumed manually with 'drbdadm resume-io'.

--ko-count number
If a secondary node fails to complete a write request in ko-count times the
timeout parameter, it is excluded from the cluster. The primary node then sets the
connection to this secondary node to Standalone. To disable this feature, you
should explicitly set it to 0; defaults may change between versions.

--max-buffers number
Limits the memory usage per DRBD minor device on the receiving side, or for
internal buffers during resync or online-verify. Unit is PAGE_SIZE, which is 4 KiB
on most systems. The minimum possible setting is hard coded to 32 (=128 KiB).
These buffers are used to hold data blocks while they are written to/read from
disk. To avoid possible distributed deadlocks on congestion, this setting is used
as a throttle threshold rather than a hard limit. Once more than max-buffers pages
are in use, further allocation from this pool is throttled. You want to increase
max-buffers if you cannot saturate the IO backend on the receiving side.

--max-epoch-size number
Define the maximum number of write requests DRBD may issue before issuing a write
barrier. The default value is 2048, with a minimum of 1 and a maximum of 20000.
Setting this parameter to a value below 10 is likely to decrease performance.

--on-congestion policy,
--congestion-fill threshold,
--congestion-extents threshold
By default, DRBD blocks when the TCP send queue is full. This prevents
applications from generating further write requests until more buffer space
becomes available again.

When DRBD is used together with DRBD-proxy, it can be better to use the pull-ahead
on-congestion policy, which can switch DRBD into ahead/behind mode before the send
queue is full. DRBD then records the differences between itself and the peer in
its bitmap, but it no longer replicates them to the peer. When enough buffer space
becomes available again, the node resynchronizes with the peer and switches back
to normal replication.

This has the advantage of not blocking application I/O even when the queues fill
up, and the disadvantage that peer nodes can fall behind much further. Also, while
resynchronizing, peer nodes will become inconsistent.

The available congestion policies are block (the default) and pull-ahead. The
congestion-fill parameter defines how much data is allowed to be "in flight" in
this connection. The default value is 0, which disables this mechanism of
congestion control, with a maximum of 10 GiBytes. The congestion-extents parameter
defines how many bitmap extents may be active before switching into ahead/behind
mode, with the same default and limits as the al-extents parameter. The
congestion-extents parameter is effective only when set to a value smaller than
al-extents.

Ahead/behind mode is available since DRBD 8.3.10.

--ping-int interval
When the TCP/IP connection to a peer is idle for more than ping-int seconds, DRBD
will send a keep-alive packet to make sure that a failed peer or network
connection is detected reasonably soon. The default value is 10 seconds, with a
minimum of 1 and a maximum of 120 seconds. The unit is seconds.

--ping-timeout timeout
Define the timeout for replies to keep-alive packets. If the peer does not reply
within ping-timeout, DRBD will close and try to reestablish the connection. The
default value is 0.5 seconds, with a minimum of 0.1 seconds and a maximum of 3
seconds. The unit is tenths of a second.

--socket-check-timeout timeout
In setups involving a DRBD-proxy and connections that experience a lot of
buffer-bloat it might be necessary to set ping-timeout to an unusual high value.
By default DRBD uses the same value to wait if a newly established TCP-connection
is stable. Since the DRBD-proxy is usually located in the same data center such a
long wait time may hinder DRBD's connect process.

In such setups socket-check-timeout should be set to at least to the round trip
time between DRBD and DRBD-proxy. I.e. in most cases to 1.

The default unit is tenths of a second, the default value is 0 (which causes DRBD
to use the value of ping-timeout instead). Introduced in 8.4.5.

--protocol name
Use the specified protocol on this connection. The supported protocols are:

A
Writes to the DRBD device complete as soon as they have reached the local disk
and the TCP/IP send buffer.

B
Writes to the DRBD device complete as soon as they have reached the local
disk, and all peers have acknowledged the receipt of the write requests.

C
Writes to the DRBD device complete as soon as they have reached the local and
all remote disks.

--rcvbuf-size size
Configure the size of the TCP/IP receive buffer. A value of 0 (the default) causes
the buffer size to adjust dynamically. This parameter usually does not need to be
set, but it can be set to a value up to 10 MiB. The default unit is bytes.

--rr-conflict policy
This option helps to solve the cases when the outcome of the resync decision is
incompatible with the current role assignment in the cluster. The defined policies
are:

disconnect
No automatic resynchronization, simply disconnect.

retry-connect
Disconnect now, and retry to connect immediatly afterwards.

violently
Resync to the primary node is allowed, violating the assumption that data on a
block device are stable for one of the nodes. Do not use this option, it is
dangerous.

call-pri-lost
Call the pri-lost handler on one of the machines. The handler is expected to
reboot the machine, which puts it into secondary role.

--shared-secret secret
Configure the shared secret used for peer authentication. The secret is a string
of up to 64 characters. Peer authentication also requires the cram-hmac-alg
parameter to be set.

--sndbuf-size size
Configure the size of the TCP/IP send buffer. Since DRBD 8.0.13 / 8.2.7, a value
of 0 (the default) causes the buffer size to adjust dynamically. Values below 32
KiB are harmful to the throughput on this connection. Large buffer sizes can be
useful especially when protocol A is used over high-latency networks; the maximum
value supported is 10 MiB.

--tcp-cork
By default, DRBD uses the TCP_CORK socket option to prevent the kernel from
sending partial messages; this results in fewer and bigger packets on the network.
Some network stacks can perform worse with this optimization. On these, the
tcp-cork parameter can be used to turn this optimization off.

--timeout time
Define the timeout for replies over the network: if a peer node does not send an
expected reply within the specified timeout, it is considered dead and the TCP/IP
connection is closed. The timeout value must be lower than connect-int and lower
than ping-int. The default is 6 seconds; the value is specified in tenths of a
second.

--use-rle
Each replicated device on a cluster node has a separate bitmap for each of its
peer devices. The bitmaps are used for tracking the differences between the local
and peer device: depending on the cluster state, a disk range can be marked as
different from the peer in the device's bitmap, in the peer device's bitmap, or in
both bitmaps. When two cluster nodes connect, they exchange each other's bitmaps,
and they each compute the union of the local and peer bitmap to determine the
overall differences.

Bitmaps of very large devices are also relatively large, but they usually compress
very well using run-length encoding. This can save time and bandwidth for the
bitmap transfers.

The use-rle parameter determines if run-length encoding should be used. It is on
by default since DRBD 8.4.0.

--verify-alg hash-algorithm
Online verification (drbdadm verify) computes and compares checksums of disk
blocks (i.e., hash values) in order to detect if they differ. The verify-alg
parameter determines which algorithm to use for these checksums. It must be set to
one of the secure hash algorithms supported by the kernel before online verify can
be used; see the shash algorithms listed in /proc/crypto.

We recommend to schedule online verifications regularly during low-load periods,
for example once a month. Also see the notes on data integrity below.

drbdsetup new-path resource peer_node_id local-addr remote-addr
The new-path command creates a path within a connection. The connection must have been
created with drbdsetup new-peer. Local_addr and remote_addr refer to the local and
remote protocol, network address, and port in the format
[address-family:]address[:port]. The address families ipv4, ipv6, ssocks (Dolphin
Interconnect Solutions' "super sockets"), sdp (Infiniband Sockets Direct Protocol),
and sci are supported (sci is an alias for ssocks). If no address family is specified,
ipv4 is assumed. For all address families except ipv6, the address uses IPv4 address
notation (for example, 1.2.3.4). For ipv6, the address is enclosed in brackets and
uses IPv6 address notation (for example, [fd01:2345:6789:abcd::1]). The port defaults
to 7788.

drbdsetup connect resource peer_node_id
The connect command activates a connection. That means that the DRBD driver will bind
and listen on all local addresses of the connection-'s paths. It will begin to try to
establish one or more paths of the connection. Available options:

--tentative
Only determine if a connection to the peer can be established and if a resync is
necessary (and in which direction) without actually establishing the connection or
starting the resync. Check the system log to see what DRBD would do without the
--tentative option.

--discard-my-data
Discard the local data and resynchronize with the peer that has the most
up-to-data data. Use this option to manually recover from a split-brain situation.

drbdsetup del-peer resource peer_node_id
The del-peer command removes a connection from a resource.

drbdsetup del-path resource peer_node_id local-addr remote-addr
The del-path command removes a path from a connection. Please note that it fails if
the path is necessary to keep a connected connection in tact. In order to remove all
paths, disconnect the connection first.

drbdsetup cstate resource peer_node_id
Show the current state of a connection. The connection is identified by the node-id of
the peer; see the drbdsetup connect command.

drbdsetup del-minor minor
Remove a replicated device. No lower-level device may be attached; see drbdsetup
detach.

drbdsetup del-resource resource
Remove a resource. All volumes and connections must be removed first (drbdsetup
del-minor, drbdsetup disconnect). Alternatively, drbdsetup down can be used to remove
a resource together with all its volumes and connections.

drbdsetup detach minor
Detach the lower-level device of a replicated device. Available options:

--force
Force the detach and return immediately. This puts the lower-level device into
failed state until all pending I/O has completed, and then detaches the device.
Any I/O not yet submitted to the lower-level device (for example, because I/O on
the device was suspended) is assumed to have failed.

drbdsetup disconnect resource peer_node_id
Remove a connection to a peer host. The connection is identified by the node-id of the
peer; see the drbdsetup connect command.

drbdsetup down {resource | all}
Take a resource down by removing all volumes, connections, and the resource itself.

drbdsetup dstate minor
Show the current disk state of a lower-level device.

drbdsetup events2 {resource | all}
Show the current state of all configured DRBD objects, followed by all changes to the
state.

The output format is meant to be human as well as machine readable. The line starts
with a word that indicates the kind of event: exists for an existing object; create,
destroy, and change if an object is created, destroyed, or changed; or call or
response if an event handler is called or it returns. The second word indicates the
object the event applies to: resource, device, connection, peer-device, path, helper,
or a dash (-) to indicate that the current state has been dumped completely.

The remaining words identify the object and describe the state that the object is in.
Some special keys are worth mentioning:

resource may_promote:{yes|no}
Whether promoting to primary is expected to succeed. When quorum is enabled, this
can be used to trigger failover. When may_promote:yes is reported on this node,
then no writes are possible on any other node, which generally means that the
application can be started on this node, even when it has been running on another.

resource promotion_score:score
An integer heuristic indicating the relative preference for promoting this
resource. A higher score is better in terms of having local disks and having
access to up-to-date data. The score may be positive even when some node is
primary. It will be zero when promotion is impossible due to quorum or lack of any
access to up-to-date data.

Available options:

--now
Terminate after reporting the current state. The default is to continuously listen
and report state changes.

--poll
This is completely ignored if --now is not given. In combination with --now it
prints the current state once and then reads on stdin. If a n is read, this
triggers another run. Newlines are ignored. Every other input terminates the
command.

--statistics
Include statistics in the output.

drbdsetup get-gi resource peer_node_id volume
Show the data generation identifiers for a device on a particular connection. The
device is identified by its volume number. The connection is identified by its
endpoints; see the drbdsetup connect command.

The output consists of the current UUID, bitmap UUID, and the first two history UUIDS,
folowed by a set of flags. The current UUID and history UUIDs are device specific; the
bitmap UUID and flags are peer device specific. This command only shows the first two
history UUIDs. Internally, DRBD maintains one history UUID for each possible peer
device.

drbdsetup invalidate minor
Replace the local data of a device with that of a peer. All the local data will be
marked out-of-sync, and a resync with the specified peer device will be initialted.

drbdsetup invalidate-remote resource peer_node_id volume
Replace a peer device's data of a resource with the local data. The peer device's data
will be marked out-of-sync, and a resync from the local node to the specified peer
will be initiated.

drbdsetup new-current-uuid minor
Generate a new current UUID and rotates all other UUID values. This has at least two
use cases, namely to skip the initial sync, and to reduce network bandwidth when
starting in a single node configuration and then later (re-)integrating a remote site.

Available option:

--clear-bitmap
Clears the sync bitmap in addition to generating a new current UUID.

This can be used to skip the initial sync, if you want to start from scratch. This
use-case does only work on "Just Created" meta data. Necessary steps:

1. On both nodes, initialize meta data and configure the device.

drbdadm create-md --force res/volume-number

2. They need to do the initial handshake, so they know their sizes.

drbdadm up res

3. They are now Connected Secondary/Secondary Inconsistent/Inconsistent. Generate a
new current-uuid and clear the dirty bitmap.

drbdadm --clear-bitmap new-current-uuid res

4. They are now Connected Secondary/Secondary UpToDate/UpToDate. Make one side
primary and create a file system.

drbdadm primary res

mkfs -t fs-type $(drbdadm sh-dev res)

One obvious side-effect is that the replica is full of old garbage (unless you made
them identical using other means), so any online-verify is expected to find any number
of out-of-sync blocks.

You must not use this on pre-existing data! Even though it may appear to work at
first glance, once you switch to the other node, your data is toast, as it never got
replicated. So do not leave out the mkfs (or equivalent).

This can also be used to shorten the initial resync of a cluster where the second node
is added after the first node is gone into production, by means of disk shipping. This
use-case works on disconnected devices only, the device may be in primary or secondary
role.

The necessary steps on the current active server are:

1. drbdsetup new-current-uuid --clear-bitmap minor

2. Take the copy of the current active server. E.g. by pulling a disk out of the
RAID1 controller, or by copying with dd. You need to copy the actual data, and the
meta data.

3. drbdsetup new-current-uuid minor

Now add the disk to the new secondary node, and join it to the cluster. You will get a
resync of that parts that were changed since the first call to drbdsetup in step 1.

drbdsetup new-minor resource minor volume
Create a new replicated device within a resource. The command creates a block device
inode for the replicated device (by default, /dev/drbdminor). The volume number
identifies the device within the resource.

drbdsetup new-resource resource node_id,
drbdsetup resource-options resource
The new-resource command creates a new resource. The resource-options command changes
the resource options of an existing resource. Available options:

--auto-promote bool-value
A resource must be promoted to primary role before any of its devices can be
mounted or opened for writing.

Before DRBD 9, this could only be done explicitly ("drbdadm primary"). Since DRBD
9, the auto-promote parameter allows to automatically promote a resource to
primary role when one of its devices is mounted or opened for writing. As soon as
all devices are unmounted or closed with no more remaining users, the role of the
resource changes back to secondary.

Automatic promotion only succeeds if the cluster state allows it (that is, if an
explicit drbdadm primary command would succeed). Otherwise, mounting or opening
the device fails as it already did before DRBD 9: the mount(2) system call fails
with errno set to EROFS (Read-only file system); the open(2) system call fails
with errno set to EMEDIUMTYPE (wrong medium type).

Irrespective of the auto-promote parameter, if a device is promoted explicitly
(drbdadm primary), it also needs to be demoted explicitly (drbdadm secondary).

The auto-promote parameter is available since DRBD 9.0.0, and defaults to yes.

--cpu-mask cpu-mask
Set the cpu affinity mask for DRBD kernel threads. The cpu mask is specified as a
hexadecimal number. The default value is 0, which lets the scheduler decide which
kernel threads run on which CPUs. CPU numbers in cpu-mask which do not exist in
the system are ignored.

--on-no-data-accessible policy
Determine how to deal with I/O requests when the requested data is not available
locally or remotely (for example, when all disks have failed). The defined
policies are:

io-error
System calls fail with errno set to EIO.

suspend-io
The resource suspends I/O. I/O can be resumed by (re)attaching the lower-level
device, by connecting to a peer which has access to the data, or by forcing
DRBD to resume I/O with drbdadm resume-io res. When no data is available,
forcing I/O to resume will result in the same behavior as the io-error policy.

This setting is available since DRBD 8.3.9; the default policy is io-error.

--peer-ack-window value
On each node and for each device, DRBD maintains a bitmap of the differences
between the local and remote data for each peer device. For example, in a
three-node setup (nodes A, B, C) each with a single device, every node maintains
one bitmap for each of its peers.

When nodes receive write requests, they know how to update the bitmaps for the
writing node, but not how to update the bitmaps between themselves. In this
example, when a write request propagates from node A to B and C, nodes B and C
know that they have the same data as node A, but not whether or not they both have
the same data.

As a remedy, the writing node occasionally sends peer-ack packets to its peers
which tell them which state they are in relative to each other.

The peer-ack-window parameter specifies how much data a primary node may send
before sending a peer-ack packet. A low value causes increased network traffic; a
high value causes less network traffic but higher memory consumption on secondary
nodes and higher resync times between the secondary nodes after primary node
failures. (Note: peer-ack packets may be sent due to other reasons as well, e.g.
membership changes or expiry of the peer-ack-delay timer.)

The default value for peer-ack-window is 2 MiB, the default unit is sectors. This
option is available since 9.0.0.

--peer-ack-delay expiry-time
If after the last finished write request no new write request gets issued for
expiry-time, then a peer-ack packet is sent. If a new write request is issued
before the timer expires, the timer gets reset to expiry-time. (Note: peer-ack
packets may be sent due to other reasons as well, e.g. membership changes or the
peer-ack-window option.)

This parameter may influence resync behavior on remote nodes. Peer nodes need to
wait until they receive an peer-ack for releasing a lock on an AL-extent. Resync
operations between peers may need to wait for for these locks.

The default value for peer-ack-delay is 100 milliseconds, the default unit is
milliseconds. This option is available since 9.0.0.

--quorum value
When activated, a cluster partition requires quorum in order to modify the
replicated data set. That means a node in the cluster partition can only be
promoted to primary if the cluster partition has quorum. Every node with a disk
directly connected to the node that should be promoted counts. If a primary node
should execute a write request, but the cluster partition has lost quorum, it will
freeze IO or reject the write request with an error (depending on the on-no-quorum
setting). Upon loosing quorum a primary always invokes the quorum-lost handler.
The handler is intended for notification purposes, its return code is ignored.

The option's value might be set to off, majority, all or a numeric value. If you
set it to a numeric value, make sure that the value is greater than half of your
number of nodes. Quorum is a mechanism to avoid data divergence, it might be used
instead of fencing when there are more than two repicas. It defaults to off

If all missing nodes are marked as outdated, a partition always has quorum, no
matter how small it is. I.e. If you disconnect all secondary nodes gracefully a
single primary continues to operate. In the moment a single secondary is lost, it
has to be assumed that it forms a partition with all the missing outdated nodes.
In case my partition might be smaller than the other, quorum is lost in this
moment.

In case you want to allow permanently diskless nodes to gain quorum it is
recommendet to not use majority or all. It is recommended to specify an absolute
number, since DBRD's heuristic to determine the complete number of diskfull nodes
in the cluster is unreliable.

The quorum implementation is available starting with the DRBD kernel driver
version 9.0.7.

--quorum-minimum-redundancy value
This option sets the minimal required number of nodes with an UpToDate disk to
allow the partition to gain quorum. This is a different requirement than the plain
quorum option expresses.

The option's value might be set to off, majority, all or a numeric value. If you
set it to a numeric value, make sure that the value is greater than half of your
number of nodes.

This option is available starting with the DRBD kernel driver version 9.0.10.

--on-no-quorum {io-error | suspend-io}
By default DRBD freezes IO on a device, that lost quorum. By setting the
on-no-quorum to io-error it completes all IO operations with an error if quorum
ist lost.

The on-no-quorum options is available starting with the DRBD kernel driver version
9.0.8.

drbdsetup outdate minor
Mark the data on a lower-level device as outdated. This is used for fencing, and
prevents the resource the device is part of from becoming primary in the future. See
the --fencing disk option.

drbdsetup pause-sync resource peer_node_id volume
Stop resynchronizing between a local and a peer device by setting the local pause
flag. The resync can only resume if the pause flags on both sides of a connection are
cleared.

drbdsetup primary resource
Change the role of a node in a resource to primary. This allows the replicated devices
in this resource to be mounted or opened for writing. Available options:

--overwrite-data-of-peer
This option is an alias for the --force option.

--force
Force the resource to become primary even if some devices are not guaranteed to
have up-to-date data. This option is used to turn one of the nodes in a newly
created cluster into the primary node, or when manually recovering from a
disaster.

Note that this can lead to split-brain scenarios. Also, when forcefully turning an
inconsistent device into an up-to-date device, it is highly recommended to use any
integrity checks available (such as a filesystem check) to make sure that the
device can at least be used without crashing the system.

Note that DRBD usually only allows one node in a cluster to be in primary role at any
time; this allows DRBD to coordinate access to the devices in a resource across nodes.
The --allow-two-primaries network option changes this; in that case, a mechanism
outside of DRBD needs to coordinate device access.

drbdsetup resize minor
Reexamine the size of the lower-level devices of a replicated device on all nodes.
This command is called after the lower-level devices on all nodes have been grown to
adjust the size of the replicated device. Available options:

--assume-peer-has-space
Resize the device even if some of the peer devices are not connected at the
moment. DRBD will try to resize the peer devices when they next connect. It will
refuse to connect to a peer device which is too small.

--assume-clean
Do not resynchronize the added disk space; instead, assume that it is identical on
all nodes. This option can be used when the disk space is uninitialized and
differences do not matter, or when it is known to be identical on all nodes. See
the drbdsetup verify command.

--size val
This option can be used to online shrink the usable size of a drbd device. It's
the users responsibility to make sure that a file system on the device is not
truncated by that operation.

--al-stripes val --al-stripes val
These options may be used to change the layout of the activity log online. In case
of internal meta data this may invovle shrinking the user visible size at the same
time (unsing the --size) or increasing the avalable space on the backing devices.

drbdsetup resume-io minor
Resume I/O on a replicated device. See the --fencing net option.

drbdsetup resume-sync resource peer_node_id volume
Allow resynchronization to resume by clearing the local sync pause flag.

drbdsetup role resource
Show the current role of a resource.

drbdsetup secondary resource
Change the role of a node in a resource to secondary. This command fails if the
replicated device is in use.

drbdsetup show {resource | all}
Show the current configuration of a resource, or of all resources. Available options:

--show-defaults
Show all configuration parameters, even the ones with default values. Normally,
parameters with default values are not shown.

drbdsetup show-gi resource peer_node_id volume
Show the data generation identifiers for a device on a particular connection. In
addition, explain the output. The output otherwise is the same as in the drbdsetup
get-gi command.

drbdsetup state
This is an alias for drbdsetup role. Deprecated.

drbdsetup status {resource | all}
Show the status of a resource, or of all resources. The output consists of one
paragraph for each configured resource. Each paragraph contains one line for each
resource, followed by one line for each device, and one line for each connection. The
device and connection lines are indented. The connection lines are followed by one
line for each peer device; these lines are indented against the connection line.

Long lines are wrapped around at terminal width, and indented to indicate how the
lines belongs together. Available options:

--verbose
Include more information in the output even when it is likely redundant or
irrelevant.

--statistics
Include data transfer statistics in the output.

--color={always | auto | never}
Colorize the output. With --color=auto, drbdsetup emits color codes only when
standard output is connected to a terminal.

For example, the non-verbose output for a resource with only one connection and only
one volume could look like this:

drbd0 role:Primary
disk:UpToDate
host2.example.com role:Secondary
disk:UpToDate

With the --verbose option, the same resource could be reported as:

drbd0 node-id:1 role:Primary suspended:no
volume:0 minor:1 disk:UpToDate blocked:no
host2.example.com local:ipv4:192.168.123.4:7788
peer:ipv4:192.168.123.2:7788 node-id:0 connection:WFReportParams
role:Secondary congested:no
volume:0 replication:Connected disk:UpToDate resync-suspended:no

drbdsetup suspend-io minor
Suspend I/O on a replicated device. It is not usually necessary to use this command.

drbdsetup verify resource peer_node_id volume
Start online verification, change which part of the device will be verified, or stop
online verification. The command requires the specified peer to be connected.

Online verification compares each disk block on the local and peer node. Blocks which
differ between the nodes are marked as out-of-sync, but they are not automatically
brought back into sync. To bring them into sync, the resource must be disconnected and
reconnected. Progress can be monitored in the output of drbdsetup status --statistics.
Available options:

--start position
Define where online verification should start. This parameter is ignored if online
verification is already in progress. If the start parameter is not specified,
online verification will continue where it was interrupted (if the connection to
the peer was lost while verifying), after the previous stop sector (if the
previous online verification has finished), or at the beginning of the device (if
the end of the device was reached, or online verify has not run before).

The position on disk is specified in disk sectors (512 bytes) by default.

--stop position
Define where online verification should stop. If online verification is already in
progress, the stop position of the active online verification process is changed.
Use this to stop online verification.

The position on disk is specified in disk sectors (512 bytes) by default.

Also see the notes on data integrity in the drbd.conf(5) manual page.

drbdsetup wait-connect-volume resource peer_node_id volume,
drbdsetup wait-connect-connection resource peer_node_id,
drbdsetup wait-connect-resource resource,
drbdsetup wait-sync-volume resource peer_node_id volume,
drbdsetup wait-sync-connection resource peer_node_id,
drbdsetup wait-sync-resource resource
The wait-connect-* commands waits until a device on a peer is visible. The wait-sync-*
commands waits until a device on a peer is up to date. Available options for both
commands:

--degr-wfc-timeout timeout
Define how long to wait until all peers are connected in case the cluster
consisted of a single node only when the system went down. This parameter is
usually set to a value smaller than wfc-timeout. The assumption here is that peers
which were unreachable before a reboot are less likely to be reachable after the
reboot, so waiting is less likely to help.

The timeout is specified in seconds. The default value is 0, which stands for an
infinite timeout. Also see the wfc-timeout parameter.

--outdated-wfc-timeout timeout
Define how long to wait until all peers are connected if all peers were outdated
when the system went down. This parameter is usually set to a value smaller than
wfc-timeout. The assumption here is that an outdated peer cannot have become
primary in the meantime, so we don't need to wait for it as long as for a node
which was alive before.

The timeout is specified in seconds. The default value is 0, which stands for an
infinite timeout. Also see the wfc-timeout parameter.

--wait-after-sb
This parameter causes DRBD to continue waiting in the init script even when a
split-brain situation has been detected, and the nodes therefore refuse to connect
to each other.

--wfc-timeout timeout
Define how long the init script waits until all peers are connected. This can be
useful in combination with a cluster manager which cannot manage DRBD resources:
when the cluster manager starts, the DRBD resources will already be up and
running. With a more capable cluster manager such as Pacemaker, it makes more
sense to let the cluster manager control DRBD resources. The timeout is specified
in seconds. The default value is 0, which stands for an infinite timeout. Also see
the degr-wfc-timeout parameter.

drbdsetup forget-peer resource peer_node_id
The forget-peer command removes all traces of a peer node from the meta-data. It frees
a bitmap slot in the meta-data and make it avalable for futher bitmap slot allocation
in case a so-far never seen node connects.

The connection must be taken down before this command may be used. In case the peer
re-connects at a later point a bit-map based resync will be turned into a full-sync.

EXAMPLES

       Please see the DRBD User's Guide[1] for examples.

VERSION

       This document was revised for version 9.0.0 of the DRBD distribution.

AUTHOR

       Written by Philipp Reisner <philipp.reisner@linbit.com> and Lars Ellenberg
       <lars.ellenberg@linbit.com>.

REPORTING BUGS

       Report bugs to <drbd-user@lists.linbit.com>.

COPYRIGHT

       Copyright 2001-2018 LINBIT Information Technologies, Philipp Reisner, Lars Ellenberg. This
       is free software; see the source for copying conditions. There is NO warranty; not even
       for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

NOTES

        1. DRBD User's Guide
           http://www.drbd.org/users-guide/

        2. DRBD Web Site
           http://www.drbd.org/

NAME

SYNOPSIS

DESCRIPTION

COMMANDS

EXAMPLES

VERSION

AUTHOR

REPORTING BUGS

COPYRIGHT

SEE ALSO

NOTES