Provided by: drbd8-utils_8.4.4-1ubuntu1_amd64 bug

NAME

       drbdsetup - Setup tool for DRBD .

SYNOPSIS

       drbdsetup new-resource resource [--cpu-mask {val}]
                 [--on-no-data-accessible {io-error | suspend-io}]

       drbdsetup new-minor resource minor volume

       drbdsetup del-resource resource

       drbdsetup del-minor minor

       drbdsetup attach minor lower_dev meta_data_dev meta_data_index [--size {val}]
                 [--max-bio-bvecs {val}] [--on-io-error {pass_on | call-local-io-error | detach}]
                 [--fencing {dont-care | resource-only | resource-and-stonith}] [--disk-barrier]
                 [--disk-flushes] [--disk-drain] [--md-flushes] [--resync-rate {val}]
                 [--resync-after {val}] [--al-extents {val}] [--al-updates]
                 [--c-plan-ahead {val}] [--c-delay-target {val}] [--c-fill-target {val}]
                 [--c-max-rate {val}] [--c-min-rate {val}] [--disk-timeout {val}]
                 [--read-balancing {prefer-local | prefer-remote | round-robin | least-pending | when-congested-remote | 32K-striping | 64K-striping | 128K-striping | 256K-striping | 512K-striping | 1M-striping}]

       drbdsetup connect resource local_addr remote_addr [--tentative] [--discard-my-data]
                 [--protocol {A | B | C}] [--timeout {val}] [--max-epoch-size {val}]
                 [--max-buffers {val}] [--unplug-watermark {val}] [--connect-int {val}]
                 [--ping-int {val}] [--sndbuf-size {val}] [--rcvbuf-size {val}]
                 [--ko-count {val}] [--allow-two-primaries] [--cram-hmac-alg {val}]
                 [--shared-secret {val}]
                 [--after-sb-0pri {disconnect | discard-younger-primary | discard-older-primary | discard-zero-changes | discard-least-changes | discard-local | discard-remote}]
                 [--after-sb-1pri {disconnect | consensus | discard-secondary | call-pri-lost-after-sb | violently-as0p}]
                 [--after-sb-2pri {disconnect | call-pri-lost-after-sb | violently-as0p}]
                 [--always-asbp] [--rr-conflict {disconnect | call-pri-lost | violently}]
                 [--ping-timeout {val}] [--data-integrity-alg {val}] [--tcp-cork]
                 [--on-congestion {block | pull-ahead | disconnect}] [--congestion-fill {val}]
                 [--congestion-extents {val}] [--csums-alg {val}] [--verify-alg {val}]
                 [--use-rle]

       drbdsetup disk-options minor [--on-io-error {pass_on | call-local-io-error | detach}]
                 [--fencing {dont-care | resource-only | resource-and-stonith}] [--disk-barrier]
                 [--disk-flushes] [--disk-drain] [--md-flushes] [--resync-rate {val}]
                 [--resync-after {val}] [--al-extents {val}] [--al-updates]
                 [--c-plan-ahead {val}] [--c-delay-target {val}] [--c-fill-target {val}]
                 [--c-max-rate {val}] [--c-min-rate {val}] [--disk-timeout {val}]
                 [--read-balancing {prefer-local | prefer-remote | round-robin | least-pending | when-congested-remote | 32K-striping | 64K-striping | 128K-striping | 256K-striping | 512K-striping | 1M-striping}]

       drbdsetup net-options local_addr remote_addr [--protocol {A | B | C}] [--timeout {val}]
                 [--max-epoch-size {val}] [--max-buffers {val}] [--unplug-watermark {val}]
                 [--connect-int {val}] [--ping-int {val}] [--sndbuf-size {val}]
                 [--rcvbuf-size {val}] [--ko-count {val}] [--allow-two-primaries]
                 [--cram-hmac-alg {val}] [--shared-secret {val}]
                 [--after-sb-0pri {disconnect | discard-younger-primary | discard-older-primary | discard-zero-changes | discard-least-changes | discard-local | discard-remote}]
                 [--after-sb-1pri {disconnect | consensus | discard-secondary | call-pri-lost-after-sb | violently-as0p}]
                 [--after-sb-2pri {disconnect | call-pri-lost-after-sb | violently-as0p}]
                 [--always-asbp] [--rr-conflict {disconnect | call-pri-lost | violently}]
                 [--ping-timeout {val}] [--data-integrity-alg {val}] [--tcp-cork]
                 [--on-congestion {block | pull-ahead | disconnect}] [--congestion-fill {val}]
                 [--congestion-extents {val}] [--csums-alg {val}] [--verify-alg {val}]
                 [--use-rle]

       drbdsetup resource-options resource [--cpu-mask {val}]
                 [--on-no-data-accessible {io-error | suspend-io}]

       drbdsetup disconnect local_addr remote_addr [--force]

       drbdsetup detach minor [--force]

       drbdsetup primary minor [--force]

       drbdsetup secondary minor

       drbdsetup down resource

       drbdsetup verify minor [--start {val}] [--stop {val}]

       drbdsetup invalidate minor

       drbdsetup invalidate-remote minor

       drbdsetup wait-connect minor [--wfc-timeout {val}] [--degr-wfc-timeout {val}]
                 [--outdated-wfc-timeout {val}] [--wait-after-sb {val}]

       drbdsetup wait-sync minor [--wfc-timeout {val}] [--degr-wfc-timeout {val}]
                 [--outdated-wfc-timeout {val}] [--wait-after-sb {val}]

       drbdsetup role minor

       drbdsetup cstate minor

       drbdsetup dstate minor

       drbdsetup resize minor [--size {val}] [--assume-peer-has-space] [--assume-clean]
                 [--al-stripes {val}] [--al-stripe-size-kB {val}]

       drbdsetup check-resize minor

       drbdsetup pause-sync minor

       drbdsetup resume-sync minor

       drbdsetup outdate minor

       drbdsetup show-gi minor

       drbdsetup get-gi minor

       drbdsetup show {resource | minor | all}

       drbdsetup suspend-io minor

       drbdsetup resume-io minor

       drbdsetup events {resource | minor | all}

       drbdsetup new-current-uuid minor [--clear-bitmap]

DESCRIPTION

       drbdsetup is used to associate DRBD devices with their backing block devices, to set up
       DRBD device pairs to mirror their backing block devices, and to inspect the configuration
       of running DRBD devices.

NOTE

       drbdsetup is a low level tool of the DRBD program suite. It is used by the data disk and
       drbd scripts to communicate with the device driver.

COMMANDS

       Each drbdsetup sub-command might require arguments and bring its own set of options. All
       values have default units which might be overruled by K, M or G. These units are defined
       in the usual way (e.g. K = 2^10 = 1024).

   Common options
       All drbdsetup sub-commands accept these two options

       --create-device
           In case the specified DRBD device (minor number) does not exist yet, create it
           implicitly.

   new-resource
       Resources are the primary objects of any DRBD configuration. A resource must be created
       with the new-resource command before any volumes or minor devices can be created.
       Connections are referenced by name.

   new-minor
       A minor is used as a synonym for replicated block device. It is represented in the /dev/
       directory by a block device. It is the application's interface to the DRBD-replicated
       block devices. These block devices get addressed by their minor numbers on the drbdsetup
       commandline.

       A pair of replicated block devices may have different minor numbers on the two machines.
       They are associated by a common volume-number. Volume numbers are local to each
       connection. Minor numbers are global on one node.

   del-resource
       Destroys a resource object. This is only possible if the resource has no volumes.

   del-minor
       Minors can only be destroyed if its disk is detached.

   attach, disk-options
       Attach associates device with lower_device to store its data blocks on. The -d (or
       --disk-size) should only be used if you wish not to use as much as possible from the
       backing block devices. If you do not use -d, the device is only ready for use as soon as
       it was connected to its peer once. (See the net command.)

       With the disk-options command it is possible to change the options of a minor while it is
       attached.

       --disk-size size
           You can override DRBD's size determination method with this option. If you need to use
           the device before it was ever connected to its peer, use this option to pass the size
           of the DRBD device to the driver. Default unit is sectors (1s = 512 bytes).

           If you use the size parameter in drbd.conf, we strongly recommend to add an explicit
           unit postfix. drbdadm and drbdsetup used to have mismatching default units.

       --on-io-error err_handler
           If the driver of the lower_device reports an error to DRBD, DRBD will mark the disk as
           inconsistent, call a helper program, or detach the device from its backing storage and
           perform all further IO by requesting it from the peer. The valid err_handlers are:
           pass_on, call-local-io-error and detach.

       --fencing fencing_policy
           Under fencing we understand preventive measures to avoid situations where both nodes
           are primary and disconnected (AKA split brain).

           Valid fencing policies are:

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

           resource-only
               If a node becomes a disconnected primary, it tries to outdate the peer's disk.
               This is done by calling the fence-peer handler. The handler is supposed to reach
               the other node over alternative communication paths and call 'drbdadm outdate res'
               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 alternative communication paths and call 'drbdadm outdate res' there. In case
               it cannot reach the peer, it should stonith the peer. IO is resumed as soon as the
               situation is resolved. In case your handler fails, you can resume IO with the
               resume-io command.

       --disk-barrier, --disk-flushes, --disk-drain
           DRBD has four implementations to express write-after-write dependencies to its backing
           storage device. DRBD will use the first method that is supported by the backing
           storage device and that is not disabled. By default the flush method is used.

           Since drbd-8.4.2 disk-barrier is disabled by default because since linux-2.6.36 (or
           2.6.32 RHEL6) there is no reliable way to determine if queuing of IO-barriers works.
           Dangerous only enable if you are told so by one that knows for sure.

           When selecting the method you should not only base your decision on the measurable
           performance. In case your backing storage device has a volatile write cache (plain
           disks, RAID of plain disks) you should use one of the first two. In case your backing
           storage device has battery-backed write cache you may go with option 3. Option 4
           (disable everything, use "none") is dangerous on most IO stacks, may result in
           write-reordering, and if so, can theoretically be the reason for data corruption, or
           disturb the DRBD protocol, causing spurious disconnect/reconnect cycles.  Do not use
           no-disk-drain.

           Unfortunately device mapper (LVM) might not support barriers.

           The letter after "wo:" in /proc/drbd indicates with method is currently in use for a
           device: b, f, d, n. The implementations:

           barrier
               The first requires that the driver of the backing storage device support barriers
               (called 'tagged command queuing' in SCSI and 'native command queuing' in SATA
               speak). The use of this method can be enabled by setting the disk-barrier options
               to yes.

           flush
               The second requires that the backing device support disk flushes (called 'force
               unit access' in the drive vendors speak). The use of this method can be disabled
               setting disk-flushes to no.

           drain
               The third method is simply to let write requests drain before write requests of a
               new reordering domain are issued. That was the only implementation before 8.0.9.

           none
               The fourth method is to not express write-after-write dependencies to the backing
               store at all, by also specifying --no-disk-drain. This is dangerous on most IO
               stacks, may result in write-reordering, and if so, can theoretically be the reason
               for data corruption, or disturb the DRBD protocol, causing spurious
               disconnect/reconnect cycles.  Do not use --no-disk-drain.

       --md-flushes
           Disables the use of disk flushes and barrier BIOs when accessing the meta data device.
           See the notes on --disk-flushes.

       --max-bio-bvecs
           In some special circumstances the device mapper stack manages to pass BIOs to DRBD
           that violate the constraints that are set forth by DRBD's merge_bvec() function and
           which have more than one bvec. A known example is: phys-disk -> DRBD -> LVM -> Xen ->
           missaligned partition (63) -> DomU FS. Then you might see "bio would need to, but
           cannot, be split:" in the Dom0's kernel log.

           The best workaround is to proper align the partition within the VM (E.g. start it at
           sector 1024). That costs 480 KiB of storage. Unfortunately the default of most Linux
           partitioning tools is to start the first partition at an odd number (63). Therefore
           most distributions install helpers for virtual linux machines will end up with
           missaligned partitions. The second best workaround is to limit DRBD's max bvecs per
           BIO (i.e., the max-bio-bvecs option) to 1, but that might cost performance.

           The default value of max-bio-bvecs is 0, which means that there is no user imposed
           limitation.

       --resync-rate rate
           To ensure smooth operation of the application on top of DRBD, it is possible to limit
           the bandwidth that may be used by background synchronization. The default is 250
           KiB/sec, the default unit is KiB/sec.

       --resync-after minor
           Start resync on this device only if the device with minor is already in connected
           state. Otherwise this device waits in SyncPause state.

       --al-extents extents
           DRBD automatically performs hot area detection. With this parameter you control how
           big the hot area (=active set) can get. Each extent marks 4M of the backing storage.
           In case a primary node leaves the cluster unexpectedly, the areas covered by the
           active set must be resynced upon rejoining of the failed node. The data structure is
           stored in the meta-data area, therefore each change of the active set is a write
           operation to the meta-data device. A higher number of extents gives longer resync
           times but less updates to the meta-data. The default number of extents is 1237.
           (Minimum: 7, Maximum: 65534)

           See also drbd.conf(5) and drbdmeta(8) for additional limitations and necessary
           preparation.

       --al-updates {yes | no}
           DRBD's activity log transaction writing makes it possible, that after the crash of a
           primary node a partial (bit-map based) resync is sufficient to bring the node back to
           up-to-date. Setting al-updates to no might increase normal operation performance but
           causes DRBD to do a full resync when a crashed primary gets reconnected. The default
           value is yes.

       --c-plan-ahead plan_time, --c-fill-target fill_target, --c-delay-target delay_target,
       --c-max-rate max_rate
           The dynamic resync speed controller gets enabled with setting plan_time to a positive
           value. It aims to fill the buffers along the data path with either a constant amount
           of data fill_target, or aims to have a constant delay time of delay_target along the
           path. The controller has an upper bound of max_rate.

           By plan_time the agility of the controller is configured. Higher values yield for
           slower/lower responses of the controller to deviation from the target value. It should
           be at least 5 times RTT. For regular data paths a fill_target in the area of 4k to
           100k is appropriate. For a setup that contains drbd-proxy it is advisable to use
           delay_target instead. Only when fill_target is set to 0 the controller will use
           delay_target. 5 times RTT is a reasonable starting value.  Max_rate should be set to
           the bandwidth available between the DRBD-hosts and the machines hosting DRBD-proxy, or
           to the available disk-bandwidth.

           The default value of plan_time is 0, the default unit is 0.1 seconds.  Fill_target has
           0 and sectors as default unit.  Delay_target has 1 (100ms) and 0.1 as default unit.
           Max_rate has 10240 (100MiB/s) and KiB/s as default unit.

       --c-min-rate min_rate
           We track the disk IO rate caused by the resync, so we can detect non-resync IO on the
           lower level device. If the lower level device seems to be busy, and the current resync
           rate is above min_rate, we throttle the resync.

           The default value of min_rate is 4M, the default unit is k. If you want to not
           throttle at all, set it to zero, if you want to throttle always, set it to one.

       -t, --disk-timeout disk_timeout
           If the driver of the lower_device does not finish an IO request within disk_timeout,
           DRBD considers the disk as failed. If DRBD is connected to a remote host, it will
           reissue local pending IO requests to the peer, and ship all new IO requests to the
           peer only. The disk state advances to diskless, as soon as the backing block device
           has finished all IO requests.

           The default value of is 0, which means that no timeout is enforced. The default unit
           is 100ms. This option is available since 8.3.12.

       --read-balancing method
           The supported methods for load balancing of read requests are prefer-local,
           prefer-remote, round-robin, least-pending and when-congested-remote, 32K-striping,
           64K-striping, 128K-striping, 256K-striping, 512K-striping and 1M-striping.

           The default value of is prefer-local. This option is available since 8.4.1.

   connect, net-options
       Connect sets up the device to listen on af:local_addr:port for incoming connections and to
       try to connect to af:remote_addr:port. If port is omitted, 7788 is used as default. If af
       is omitted ipv4 gets used. Other supported address families are ipv6, ssocks for Dolphin
       Interconnect Solutions' "super sockets" and sdp for Sockets Direct Protocol (Infiniband).

       The net-options command allows you to change options while the connection is established.

       --protocol protocol
           On the TCP/IP link the specified protocol is used. Valid protocol specifiers are A, B,
           and C.

           Protocol A: write IO is reported as completed, if it has reached local disk and local
           TCP send buffer.

           Protocol B: write IO is reported as completed, if it has reached local disk and remote
           buffer cache.

           Protocol C: write IO is reported as completed, if it has reached both local and remote
           disk.

       --connect-int time
           In case it is not possible to connect to the remote DRBD device immediately, DRBD
           keeps on trying to connect. With this option you can set the time between two retries.
           The default value is 10. The unit is seconds.

       --ping-int time
           If the TCP/IP connection linking a DRBD device pair is idle for more than time
           seconds, DRBD will generate a keep-alive packet to check if its partner is still
           alive. The default value is 10. The unit is seconds.

       --timeout val
           If the partner node fails to send an expected response packet within val tenths of a
           second, the partner node is considered dead and therefore the TCP/IP connection is
           abandoned. The default value is 60 (= 6 seconds).

       --sndbuf-size size
           The socket send buffer is used to store packets sent to the secondary node, which are
           not yet acknowledged (from a network point of view) by the secondary node. When using
           protocol A, it might be necessary to increase the size of this data structure in order
           to increase asynchronicity between primary and secondary nodes. But keep in mind that
           more asynchronicity is synonymous with more data loss in the case of a primary node
           failure. Since 8.0.13 resp. 8.2.7 setting the size value to 0 means that the kernel
           should autotune this. The default size is 0, i.e. autotune.

       --rcvbuf-size size
           Packets received from the network are stored in the socket receive buffer first. From
           there they are consumed by DRBD. Before 8.3.2 the receive buffer's size was always set
           to the size of the socket send buffer. Since 8.3.2 they can be tuned independently. A
           value of 0 means that the kernel should autotune this. The default size is 0, i.e.
           autotune.

       --ko-count count
           In case the secondary node fails to complete a single write request for count times
           the timeout, it is expelled from the cluster, i.e. the primary node goes into
           StandAlone mode. The default is 0, which disables this feature.

       --max-epoch-size val
           With this option the maximal number of write requests between two barriers is limited.
           Typically set to the same as --max-buffers, or the allowed maximum. Values smaller
           than 10 can lead to degraded performance. The default value is 2048.

       --max-buffers val
           With this option the maximal number of buffer pages allocated by DRBD's receiver
           thread is limited. Typically set to the same as --max-epoch-size. Small values could
           lead to degraded performance. The default value is 2048, the minimum 32. Increase this
           if you cannot saturate the IO backend of the receiving side during linear write or
           during resync while otherwise idle.

           See also drbd.conf(5)

       --unplug-watermark val
           This setting has no effect with recent kernels that use explicit on-stack plugging
           (upstream Linux kernel 2.6.39, distributions may have backported).

           When the number of pending write requests on the standby (secondary) node exceeds the
           unplug-watermark, we trigger the request processing of our backing storage device.
           Some storage controllers deliver better performance with small values, others deliver
           best performance when the value is set to the same value as max-buffers, yet others
           don't feel much effect at all. Minimum 16, default 128, maximum 131072.

       --allow-two-primaries
           With this option set you may assign primary role to both nodes. You only should use
           this option if you use a shared storage file system on top of DRBD. At the time of
           writing the only ones are: OCFS2 and GFS. If you use this option with any other file
           system, you are going to crash your nodes and to corrupt your data!

       --cram-hmac-alg alg
           You need to specify the HMAC algorithm to enable peer authentication at all. You are
           strongly encouraged to use peer authentication. The HMAC algorithm will be used for
           the challenge response authentication of the peer. You may specify any digest
           algorithm that is named in /proc/crypto.

       --shared-secret secret
           The shared secret used in peer authentication. May be up to 64 characters.

       --after-sb-0pri asb-0p-policy
           possible policies are:

           disconnect
               No automatic resynchronization, simply disconnect.

           discard-younger-primary
               Auto sync from the node that was primary before the split-brain situation
               occurred.

           discard-older-primary
               Auto sync from the node that became primary as second during the split-brain
               situation.

           discard-zero-changes
               In case one node did not write anything since the split brain became evident, sync
               from the node that wrote something to the node that did not write anything. In
               case none wrote anything this policy uses a random decision to perform a "resync"
               of 0 blocks. In case both have written something this policy disconnects the
               nodes.

           discard-least-changes
               Auto sync from the node that touched more blocks during the split brain situation.

           discard-node-NODENAME
               Auto sync to the named node.

       --after-sb-1pri asb-1p-policy
           possible policies are:

           disconnect
               No automatic resynchronization, simply disconnect.

           consensus
               Discard the version of the secondary if the outcome of the after-sb-0pri algorithm
               would also destroy the current secondary's data. Otherwise disconnect.

           discard-secondary
               Discard the secondary's version.

           call-pri-lost-after-sb
               Always honor the outcome of the after-sb-0pri algorithm. In case it decides the
               current secondary has the correct data, call the pri-lost-after-sb on the current
               primary.

           violently-as0p
               Always honor the outcome of the after-sb-0pri algorithm. In case it decides the
               current secondary has the correct data, accept a possible instantaneous change of
               the primary's data.

       --after-sb-2pri asb-2p-policy
           possible policies are:

           disconnect
               No automatic resynchronization, simply disconnect.

           call-pri-lost-after-sb
               Always honor the outcome of the after-sb-0pri algorithm. In case it decides the
               current secondary has the right data, call the pri-lost-after-sb on the current
               primary.

           violently-as0p
               Always honor the outcome of the after-sb-0pri algorithm. In case it decides the
               current secondary has the right data, accept a possible instantaneous change of
               the primary's data.

       --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 have led to
           strange UUID sets.)

       --rr-conflict role-resync-conflict-policy
           This option sets DRBD's behavior when DRBD deduces from its meta data that a
           resynchronization is needed, and the SyncTarget node is already primary. The possible
           settings are: disconnect, call-pri-lost and violently. While disconnect speaks for
           itself, with the call-pri-lost setting the pri-lost handler is called which is
           expected to either change the role of the node to secondary, or remove the node from
           the cluster. The default is disconnect.

           With the violently setting you allow DRBD to force a primary node into SyncTarget
           state. This means that the data exposed by DRBD changes to the SyncSource's version of
           the data instantaneously. USE THIS OPTION ONLY IF YOU KNOW WHAT YOU ARE DOING.

       --data-integrity-alg hash_alg
           DRBD can ensure the data integrity of the user's data on the network by comparing hash
           values. Normally this is ensured by the 16 bit checksums in the headers of TCP/IP
           packets. This option can be set to any of the kernel's data digest algorithms. In a
           typical kernel configuration you should have at least one of md5, sha1, and crc32c
           available. By default this is not enabled.

           See also the notes on data integrity on the drbd.conf manpage.

       --no-tcp-cork
           DRBD usually uses the TCP socket option TCP_CORK to hint to the network stack when it
           can expect more data, and when it should flush out what it has in its send queue.
           There is at least one network stack that performs worse when one uses this hinting
           method. Therefore we introduced this option, which disable the setting and clearing of
           the TCP_CORK socket option by DRBD.

       --ping-timeout ping_timeout
           The time the peer has to answer to a keep-alive packet. In case the peer's reply is
           not received within this time period, it is considered dead. The default unit is
           tenths of a second, the default value is 5 (for half a second).

       --discard-my-data
           Use this option to manually recover from a split-brain situation. In case you do not
           have any automatic after-split-brain policies selected, the nodes refuse to connect.
           By passing this option you make this node a sync target immediately after successful
           connect.

       --tentative
           Causes DRBD to abort the connection process after the resync handshake, i.e. no resync
           gets performed. You can find out which resync DRBD would perform by looking at the
           kernel's log file.

       --on-congestion congestion_policy, --congestion-fill fill_threshold, --congestion-extents
       active_extents_threshold
           By default DRBD blocks when the available TCP send queue becomes full. That means it
           will slow down the application that generates the write requests that cause DRBD to
           send more data down that TCP connection.

           When DRBD is deployed with DRBD-proxy it might be more desirable that DRBD goes into
           AHEAD/BEHIND mode shortly before the send queue becomes full. In AHEAD/BEHIND mode
           DRBD does no longer replicate data, but still keeps the connection open.

           The advantage of the AHEAD/BEHIND mode is that the application is not slowed down,
           even if DRBD-proxy's buffer is not sufficient to buffer all write requests. The
           downside is that the peer node falls behind, and that a resync will be necessary to
           bring it back into sync. During that resync the peer node will have an inconsistent
           disk.

           Available congestion_policys are block and pull-ahead. The default is block.
           Fill_threshold might be in the range of 0 to 10GiBytes. The default is 0 which
           disables the check.  Active_extents_threshold has the same limits as al-extents.

           The AHEAD/BEHIND mode and its settings are available since DRBD 8.3.10.

       --verify-alg hash-alg
           During online verification (as initiated by the verify sub-command), rather than doing
           a bit-wise comparison, DRBD applies a hash function to the contents of every block
           being verified, and compares that hash with the peer. This option defines the hash
           algorithm being used for that purpose. It can be set to any of the kernel's data
           digest algorithms. In a typical kernel configuration you should have at least one of
           md5, sha1, and crc32c available. By default this is not enabled; you must set this
           option explicitly in order to be able to use on-line device verification.

           See also the notes on data integrity on the drbd.conf manpage.

       --csums-alg hash-alg
           A resync process sends all marked data blocks form the source to the destination node,
           as long as no csums-alg is given. When one is specified the resync process exchanges
           hash values of all marked blocks first, and sends only those data blocks over, that
           have different hash values.

           This setting is useful for DRBD setups with low bandwidth links. During the restart of
           a crashed primary node, all blocks covered by the activity log are marked for resync.
           But a large part of those will actually be still in sync, therefore using csums-alg
           will lower the required bandwidth in exchange for CPU cycles.

       --use-rle
           During resync-handshake, the dirty-bitmaps of the nodes are exchanged and merged
           (using bit-or), so the nodes will have the same understanding of which blocks are
           dirty. On large devices, the fine grained dirty-bitmap can become large as well, and
           the bitmap exchange can take quite some time on low-bandwidth links.

           Because the bitmap typically contains compact areas where all bits are unset (clean)
           or set (dirty), a simple run-length encoding scheme can considerably reduce the
           network traffic necessary for the bitmap exchange.

           For backward compatibility reasons, and because on fast links this possibly does not
           improve transfer time but consumes cpu cycles, this defaults to off.

           Introduced in 8.3.2.

   resource-options
       Changes the options of the resource at runtime.

       --cpu-mask cpu-mask
           Sets the cpu-affinity-mask for DRBD's kernel threads of this device. The default value
           of cpu-mask is 0, which means that DRBD's kernel threads should be spread over all
           CPUs of the machine. This value must be given in hexadecimal notation. If it is too
           big it will be truncated.

       --on-no-data-accessible ond-policy
           This setting controls what happens to IO requests on a degraded, disk less node (I.e.
           no data store is reachable). The available policies are io-error and suspend-io.

           If ond-policy is set to suspend-io you can either resume IO by attaching/connecting
           the last lost data storage, or by the drbdadm resume-io res command. The latter will
           result in IO errors of course.

           The default is io-error. This setting is available since DRBD 8.3.9.

   primary
       Sets the device into primary role. This means that applications (e.g. a file system) may
       open the device for read and write access. Data written to the device in primary role are
       mirrored to the device in secondary role.

       Normally it is not possible to set both devices of a connected DRBD device pair to primary
       role. By using the --allow-two-primaries option, you override this behavior and instruct
       DRBD to allow two primaries.

       --overwrite-data-of-peer
           Alias for --force.

       --force
           Becoming primary fails if the local replica is not up-to-date. I.e. when it is
           inconsistent, outdated of consistent. By using this option you can force it into
           primary role anyway. USE THIS OPTION ONLY IF YOU KNOW WHAT YOU ARE DOING.

   secondary
       Brings the device into secondary role. This operation fails as long as at least one
       application (or file system) has opened the device.

       It is possible that both devices of a connected DRBD device pair are secondary.

   verify
       This initiates on-line device verification. During on-line verification, the contents of
       every block on the local node are compared to those on the peer node. Device verification
       progress can be monitored via /proc/drbd. Any blocks whose content differs from that of
       the corresponding block on the peer node will be marked out-of-sync in DRBD's on-disk
       bitmap; they are not brought back in sync automatically. To do that, simply disconnect and
       reconnect the resource.

       If on-line verification is already in progress (and this node is "VerifyS"), this command
       silently "succeeds". In this case, any start-sector (see below) will be ignored, and any
       stop-sector (see below) will be honored. This can be used to stop a running verify, or to
       update/shorten/extend the coverage of the currently running verify.

       This command will fail if the device is not part of a connected device pair.

       See also the notes on data integrity on the drbd.conf manpage.

       --start start-sector
           Since version 8.3.2, on-line verification should resume from the last position after
           connection loss. It may also be started from an arbitrary position by setting this
           option. If you had reached some stop-sector before, and you do not specify an explicit
           start-sector, verify should resume from the previous stop-sector.

           Default unit is sectors. You may also specify a unit explicitly. The start-sector will
           be rounded down to a multiple of 8 sectors (4kB).

       -S, --stop stop-sector
           Since version 8.3.14, on-line verification can be stopped before it reaches
           end-of-device.

           Default unit is sectors. You may also specify a unit explicitly. The stop-sector may
           be updated by issuing an additional drbdsetup verify command on the same node while
           the verify is running. This can be used to stop a running verify, or to
           update/shorten/extend the coverage of the currently running verify.

   invalidate
       This forces the local device of a pair of connected DRBD devices into SyncTarget state,
       which means that all data blocks of the device are copied over from the peer.

       This command will fail if the device is not either part of a connected device pair, or
       disconnected Secondary.

   invalidate-remote
       This forces the local device of a pair of connected DRBD devices into SyncSource state,
       which means that all data blocks of the device are copied to the peer.

       On a disconnected Primary device, this will set all bits in the out of sync bitmap. As a
       side affect this suspends updates to the on disk activity log. Updates to the on disk
       activity log resume automatically when necessary.

   wait-connect
       Returns as soon as the device can communicate with its partner device.

       --wfc-timeout wfc_timeout, --degr-wfc-timeout degr_wfc_timeout, --outdated-wfc-timeout
       outdated_wfc_timeout, --wait-after-sb
           This command will fail if the device cannot communicate with its partner for timeout
           seconds. If the peer was working before this node was rebooted, the wfc_timeout is
           used. If the peer was already down before this node was rebooted, the degr_wfc_timeout
           is used. If the peer was successfully outdated before this node was rebooted the
           outdated_wfc_timeout is used. The default value for all those timeout values is 0
           which means to wait forever. The unit is seconds. In case the connection status goes
           down to StandAlone because the peer appeared but the devices had a split brain
           situation, the default for the command is to terminate. You can change this behavior
           with the --wait-after-sb option.

   wait-sync
       Returns as soon as the device leaves any synchronization into connected state. The options
       are the same as with the wait-connect command.

   disconnect
       Removes the information set by the net command from the device. This means that the device
       goes into unconnected state and will no longer listen for incoming connections.

   detach
       Removes the information set by the disk command from the device. This means that the
       device is detached from its backing storage device.

       -f, --force
           A regular detach returns after the disk state finally reached diskless. As a
           consequence detaching from a frozen backing block device never terminates.

           On the other hand A forced detach returns immediately. It allows you to detach DRBD
           from a frozen backing block device. Please note that the disk will be marked as failed
           until all pending IO requests where finished by the backing block device.

   down
       Removes all configuration information from the device and forces it back to unconfigured
       state.

   role
       Shows the current roles of the device and its peer, as local/peer.

   state
       Deprecated alias for "role"

   cstate
       Shows the current connection state of the device.

   dstate
       Shows the current states of the backing storage devices, as local/peer.

   resize
       This causes DRBD to reexamine the size of the device's backing storage device. To actually
       do online growing you need to extend the backing storages on both devices and call the
       resize command on one of your nodes.

       The --size 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.

       The --assume-peer-has-space allows you to resize a device which is currently not connected
       to the peer. Use with care, since if you do not resize the peer's disk as well, further
       connect attempts of the two will fail.

       When the --assume-clean option is given DRBD will skip the resync of the new storage. Only
       do this if you know that the new storage was initialized to the same content by other
       means.

       The options --al-stripes and --al-stripe-size-kB 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.

   check-resize
       To enable DRBD to detect offline resizing of backing devices this command may be used to
       record the current size of backing devices. The size is stored in files in /var/lib/drbd/
       named drbd-minor-??.lkbd

       This command is called by drbdadm resize res after drbdsetup device resize returned.

   pause-sync
       Temporarily suspend an ongoing resynchronization by setting the local pause flag. Resync
       only progresses if neither the local nor the remote pause flag is set. It might be
       desirable to postpone DRBD's resynchronization after eventual resynchronization of the
       backing storage's RAID setup.

   resume-sync
       Unset the local sync pause flag.

   outdate
       Mark the data on the local backing storage as outdated. An outdated device refuses to
       become primary. This is used in conjunction with fencing and by the peer's fence-peer
       handler.

   show-gi
       Displays the device's data generation identifiers verbosely.

   get-gi
       Displays the device's data generation identifiers.

   show
       Shows all available configuration information of the device.

   suspend-io
       This command is of no apparent use and just provided for the sake of completeness.

   resume-io
       If the fence-peer handler fails to stonith the peer node, and your fencing policy is set
       to resource-and-stonith, you can unfreeze IO operations with this command.

   events
       Displays every state change of DRBD and all calls to helper programs. This might be used
       to get notified of DRBD's state changes by piping the output to another program.

       --all-devices
           Display the events of all DRBD minors.

       --unfiltered
           This is a debugging aid that displays the content of all received netlink messages.

   new-current-uuid
       Generates 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

        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 new-current-uuid --clear-bitmap 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.

EXAMPLES

       For examples, please have a look at the DRBD User's Guide[1].

VERSION

       This document was revised for version 8.3.2 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 2001-2008 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.

SEE ALSO

       drbd.conf(5), drbd(8), drbddisk(8), drbdadm(8), DRBD User's Guide[1], DRBD web site[2]

NOTES

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

        2. DRBD web site
           http://www.drbd.org/