Provided by: openafs-fileserver_1.6.7-1ubuntu1.1_amd64 
NAME
dafileserver - Initializes the File Server component of the dafs process
SYNOPSIS
dafileserver
[-auditlog <path to log file>]
[-audit-interface (file | sysvmq)]
[-d <debug level>]
[-p <number of processes>]
[-spare <number of spare blocks>]
[-pctspare <percentage spare>]
[-b <buffers>]
[-l <large vnodes>]
[-s <small vnodes>]
[-vc <volume cachesize>]
[-w <call back wait interval>]
[-cb <number of call backs>]
[-banner]
[-novbc]
[-implicit <admin mode bits: rlidwka>]
[-readonly]
[-hr <number of hours between refreshing the host cps>]
[-busyat <redirect clients when queue > n>]
[-nobusy]
[-rxpck <number of rx extra packets>]
[-rxdbg]
[-rxdbge]
[-rxmaxmtu <bytes>]
[-nojumbo]
[-jumbo]
[-rxbind]
[-allow-dotted-principals]
[-L]
[-S]
[-k <stack size>]
[-realm <Kerberos realm name>]
[-udpsize <size of socket buffer in bytes>]
[-sendsize <size of send buffer in bytes>]
[-abortthreshold <abort threshold>]
[-enable_peer_stats]
[-enable_process_stats]
[-syslog [< loglevel >]]
[-mrafslogs]
[-saneacls]
[-help]
[-vhandle-setaside <fds reserved for non-cache io>]
[-vhandle-max-cachesize <max open files>]
[-vhandle-initial-cachesize <fds reserved for non-cache io>]
[-vattachpar <number of volume attach threads>]
[-m <min percentage spare in partition>]
[-lock]
[-fs-state-dont-save]
[-fs-state-dont-restore]
[-fs-state-verify] (none | save | restore | both)]
[-vhashsize <log(2) of number of volume hash buckets>]
[-vlrudisable]
[-vlruthresh <minutes before eligibility for soft detach>]
[-vlruinterval <seconds between VLRU scans>]
[-vlrumax <max volumes to soft detach in one VLRU scan>]
[-unsafe-nosalvage]
DESCRIPTION
The dafileserver command initializes the File Server component of the "dafs" process. In
the conventional configuration, its binary file is located in the /usr/lib/openafs
directory on a file server machine.
The dafileserver command is not normally issued at the command shell prompt, but rather
placed into a database server machine's /etc/openafs/BosConfig file with the bos create
command. If it is ever issued at the command shell prompt, the issuer must be logged onto
a file server machine as the local superuser "root".
The File Server creates the /var/log/openafs/FileLog log file as it initializes, if the
file does not already exist. It does not write a detailed trace by default, but the -d
option may be used to increase the amount of detail. Use the bos getlog command to display
the contents of the log file.
The command's arguments enable the administrator to control many aspects of the File
Server's performance, as detailed in OPTIONS. By default the File Server sets values for
many arguments that are suitable for a medium-sized file server machine. To set values
suitable for a small or large file server machine, use the -S or -L flag respectively. The
following list describes the parameters and corresponding argument for which the File
Server sets default values, and the table below summarizes the setting for each of the
three machine sizes.
• The maximum number of lightweight processes (LWPs) or pthreads the File Server uses to
handle requests for data; corresponds to the -p argument. The File Server always uses
a minimum of 32 KB of memory for these processes.
• The maximum number of directory blocks the File Server caches in memory; corresponds
to the -b argument. Each cached directory block (buffer) consumes 2,092 bytes of
memory.
• The maximum number of large vnodes the File Server caches in memory for tracking
directory elements; corresponds to the -l argument. Each large vnode consumes 292
bytes of memory.
• The maximum number of small vnodes the File Server caches in memory for tracking file
elements; corresponds to the -s argument. Each small vnode consumes 100 bytes of
memory.
• The maximum volume cache size, which determines how many volumes the File Server can
cache in memory before having to retrieve data from disk; corresponds to the -vc
argument.
• The maximum number of callback structures the File Server caches in memory;
corresponds to the -cb argument. Each callback structure consumes 16 bytes of memory.
• The maximum number of Rx packets the File Server uses; corresponds to the -rxpck
argument. Each packet consumes 1544 bytes of memory.
The default values are:
Parameter (Argument) Small (-S) Medium Large (-L)
---------------------------------------------------------------------
Number of LWPs (-p) 6 9 128
Number of cached dir blocks (-b) 70 90 120
Number of cached large vnodes (-l) 200 400 600
Number of cached small vnodes (-s) 200 400 600
Maximum volume cache size (-vc) 200 400 600
Number of callbacks (-cb) 20,000 60,000 64,000
Number of Rx packets (-rxpck) 100 150 200
To override any of the values, provide the indicated argument (which can be combined with
the -S or -L flag).
The amount of memory required for the File Server varies. The approximate default memory
usage is 751 KB when the -S flag is used (small configuration), 1.1 MB when all defaults
are used (medium configuration), and 1.4 MB when the -L flag is used (large
configuration). If additional memory is available, increasing the value of the -cb and -vc
arguments can improve File Server performance most directly.
By default, the File Server allows a volume to exceed its quota by 1 MB when an
application is writing data to an existing file in a volume that is full. The File Server
still does not allow users to create new files in a full volume. To change the default,
use one of the following arguments:
• Set the -spare argument to the number of extra kilobytes that the File Server allows
as overage. A value of 0 allows no overage.
• Set the -pctspare argument to the percentage of the volume's quota the File Server
allows as overage.
By default, the File Server implicitly grants the "a" (administer) and "l" (lookup)
permissions to system:administrators on the access control list (ACL) of every directory
in the volumes stored on its file server machine. In other words, the group's members can
exercise those two permissions even when an entry for the group does not appear on an ACL.
To change the set of default permissions, use the -implicit argument.
The File Server maintains a host current protection subgroup (host CPS) for each client
machine from which it has received a data access request. Like the CPS for a user, a host
CPS lists all of the Protection Database groups to which the machine belongs, and the File
Server compares the host CPS to a directory's ACL to determine in what manner users on the
machine are authorized to access the directory's contents. When the pts adduser or pts
removeuser command is used to change the groups to which a machine belongs, the File
Server must recompute the machine's host CPS in order to notice the change. By default,
the File Server contacts the Protection Server every two hours to recompute host CPSs,
implying that it can take that long for changed group memberships to become effective. To
change this frequency, use the -hr argument.
The File Server stores volumes in partitions. A partition is a filesystem or directory on
the server machine that is named "/vicepX" or "/vicepXX" where XX is "a" through "z" or
"aa" though "iv". Up to 255 partitions are allowed. The File Server expects that the
/vicepXX directories are each on a dedicated filesystem. The File Server will only use a
/vicepXX if it's a mountpoint for another filesystem, unless the file
"/vicepXX/AlwaysAttach" exists. A partition will not be mounted if the file
"/vicepXX/NeverAttach" exists. If both "/vicepXX/AlwaysAttach" and "/vicepXX/NeverAttach"
are present, then "/vicepXX/AlwaysAttach" wins. The data in the partition is a special
format that can only be access using OpenAFS commands or an OpenAFS client.
The File Server generates the following message when a partition is nearly full:
No space left on device
This command does not use the syntax conventions of the AFS command suites. Provide the
command name and all option names in full.
CAUTIONS
There are two strategies the File Server can use for attaching AFS volumes at startup and
handling volume salvages. The traditional method assumes all volumes are salvaged before
the File Server starts and attaches all volumes at start before serving files. The newer
demand-attach method attaches volumes only on demand, salvaging them at that time as
needed, and detaches volumes that are not in use. A demand-attach File Server can also
save state to disk for faster restarts. The dafileserver implements the demand-attach
method, while fileserver uses the traditional method.
The choice of traditional or demand-attach File Server changes the required setup in
BosConfig. When changing from a traditional File Server to demand-attach or vice versa,
you will need to stop and remove the "fs" or "dafs" node in BosConfig and create a new
node of the appropriate type. See bos_create(8) for more information.
Do not use the -k and -w arguments, which are intended for use by the OpenAFS developers
only. Changing them from their default values can result in unpredictable File Server
behavior. In any case, on many operating systems the File Server uses native threads
rather than the LWP threads, so using the -k argument to set the number of LWP threads has
no effect.
Do not specify both the -spare and -pctspare arguments. Doing so causes the File Server to
exit, leaving an error message in the /var/log/openafs/FileLog file.
Options that are available only on some system types, such as the -m and -lock options,
appear in the output generated by the -help option only on the relevant system type.
Currently, the maximum size of a volume quota is 2 terabytes (2^41 bytes) and the maximum
size of a /vicepX partition on a fileserver is 2^64 kilobytes. The maximum partition size
in releases 1.4.7 and earlier is 2 terabytes (2^31 bytes). The maximum partition size for
1.5.x releases 1.5.34 and earlier is 2 terabytes as well.
The maximum number of directory entries is 64,000 if all of the entries have names that
are 15 octets or less in length. A name that is 15 octets long requires the use of only
one block in the directory. Additional sequential blocks are required to store entries
with names that are longer than 15 octets. Each additional block provides an additional
length of 32 octets for the name of the entry. Note that if file names use an encoding
like UTF-8, a single character may be encoded into multiple octets.
In real world use, the maximum number of objects in an AFS directory is usually between
16,000 and 25,000, depending on the average name length.
OPTIONS
-auditlog <log path>
Turns on audit logging, and sets the path for the audit log. The audit log records
information about RPC calls, including the name of the RPC call, the host that
submitted the call, the authenticated entity (user) that issued the call, the
parameters for the call, and if the call succeeded or failed.
-audit-interface (file | sysvmq)
Specifies what audit interface to use. The "file" interface writes audit messages to
the file passed to -auditlog. The "sysvmq" interface writes audit messages to a SYSV
message (see msgget(2) and msgrcv(2)). The message queue the "sysvmq" interface writes
to has the key "ftok(path, 1)", where "path" is the path specified in the -auditlog
option.
Defaults to "file".
-d <debug level>
Sets the detail level for the debugging trace written to the /var/log/openafs/FileLog
file. Provide one of the following values, each of which produces an increasingly
detailed trace: 0, 1, 5, 25, and 125. The default value of 0 produces only a few
messages.
-p <number of processes>
Sets the number of threads (or LWPs) to run. Provide a positive integer. The File
Server creates and uses five threads for special purposes, in addition to the number
specified (but if this argument specifies the maximum possible number, the File Server
automatically uses five of the threads for its own purposes).
The maximum number of threads can differ in each release of OpenAFS. Consult the
OpenAFS Release Notes for the current release.
-spare <number of spare blocks>
Specifies the number of additional kilobytes an application can store in a volume
after the quota is exceeded. Provide a positive integer; a value of 0 prevents the
volume from ever exceeding its quota. Do not combine this argument with the -pctspare
argument.
-pctspare <percentage spare>
Specifies the amount by which the File Server allows a volume to exceed its quota, as
a percentage of the quota. Provide an integer between 0 and 99. A value of 0 prevents
the volume from ever exceeding its quota. Do not combine this argument with the -spare
argument.
-b <buffers>
Sets the number of directory buffers. Provide a positive integer.
-l <large vnodes>
Sets the number of large vnodes available in memory for caching directory elements.
Provide a positive integer.
-s <small nodes>
Sets the number of small vnodes available in memory for caching file elements. Provide
a positive integer.
-vc <volume cachesize>
Sets the number of volumes the File Server can cache in memory. Provide a positive
integer.
-w <call back wait interval>
Sets the interval at which the daemon spawned by the File Server performs its
maintenance tasks. Do not use this argument; changing the default value can cause
unpredictable behavior.
-cb <number of callbacks>
Sets the number of callbacks the File Server can track. Provide a positive integer.
-banner
Prints the following banner to /dev/console about every 10 minutes.
File Server is running at I<time>.
-novbc
Prevents the File Server from breaking the callbacks that Cache Managers hold on a
volume that the File Server is reattaching after the volume was offline (as a result
of the vos restore command, for example). Use of this flag is strongly discouraged.
-implicit <admin mode bits>
Defines the set of permissions granted by default to the system:administrators group
on the ACL of every directory in a volume stored on the file server machine. Provide
one or more of the standard permission letters ("rlidwka") and auxiliary permission
letters ("ABCDEFGH"), or one of the shorthand notations for groups of permissions
("all", "none", "read", and "write"). To review the meaning of the permissions, see
the fs setacl reference page.
-readonly
Don't allow writes to this fileserver.
-hr <number of hours between refreshing the host cps>
Specifies how often the File Server refreshes its knowledge of the machines that
belong to protection groups (refreshes the host CPSs for machines). The File Server
must update this information to enable users from machines recently added to
protection groups to access data for which those machines now have the necessary ACL
permissions.
-busyat <redirect clients when queue > n>
Defines the number of incoming RPCs that can be waiting for a response from the File
Server before the File Server returns the error code "VBUSY" to the Cache Manager that
sent the latest RPC. In response, the Cache Manager retransmits the RPC after a delay.
This argument prevents the accumulation of so many waiting RPCs that the File Server
can never process them all. Provide a positive integer. The default value is 600.
-rxpck <number of rx extra packets>
Controls the number of Rx packets the File Server uses to store data for incoming RPCs
that it is currently handling, that are waiting for a response, and for replies that
are not yet complete. Provide a positive integer.
-rxdbg
Writes a trace of the File Server's operations on Rx packets to the file
/var/log/openafs/rx_dbg.
-rxdbge
Writes a trace of the File Server's operations on Rx events (such as retransmissions)
to the file /var/log/openafs/rx_dbg.
-rxmaxmtu <bytes>
Defines the maximum size of an MTU. The value must be between the minimum and maximum
packet data sizes for Rx.
-jumbo
Allows the server to send and receive jumbograms. A jumbogram is a large-size packet
composed of 2 to 4 normal Rx data packets that share the same header. The fileserver
does not use jumbograms by default, as some routers are not capable of properly
breaking the jumbogram into smaller packets and reassembling them.
-nojumbo
Deprecated; jumbograms are disabled by default.
-rxbind
Force the fileserver to only bind to one IP address.
-allow-dotted-principals
By default, the RXKAD security layer will disallow access by Kerberos principals with
a dot in the first component of their name. This is to avoid the confusion where
principals user/admin and user.admin are both mapped to the user.admin PTS entry.
Sites whose Kerberos realms don't have these collisions between principal names may
disable this check by starting the server with this option.
-L Sets values for many arguments in a manner suitable for a large file server machine.
Combine this flag with any option except the -S flag; omit both flags to set values
suitable for a medium-sized file server machine.
-S Sets values for many arguments in a manner suitable for a small file server machine.
Combine this flag with any option except the -L flag; omit both flags to set values
suitable for a medium-sized file server machine.
-k <stack size>
Sets the LWP stack size in units of 1 kilobyte. Do not use this argument, and in
particular do not specify a value less than the default of 24.
-realm <Kerberos realm name>
Defines the Kerberos realm name for the File Server to use. If this argument is not
provided, it uses the realm name corresponding to the cell listed in the local
/etc/openafs/server/ThisCell file.
-udpsize <size of socket buffer in bytes>
Sets the size of the UDP buffer, which is 64 KB by default. Provide a positive
integer, preferably larger than the default.
-sendsize <size of send buffer in bytes>
Sets the size of the send buffer, which is 16384 bytes by default.
-abortthreshold <abort threshold>
Sets the abort threshold, which is triggered when an AFS client sends a number of
FetchStatus requests in a row and all of them fail due to access control or some other
error. When the abort threshold is reached, the file server starts to slow down the
responses to the problem client in order to reduce the load on the file server.
The throttling behaviour can cause issues especially for some versions of the Windows
OpenAFS client. When using Windows Explorer to navigate the AFS directory tree,
directories with only "look" access for the current user may load more slowly because
of the throttling. This is because the Windows OpenAFS client sends FetchStatus calls
one at a time instead of in bulk like the Unix Open AFS client.
Setting the threshold to 0 disables the throttling behavior. This option is available
in OpenAFS versions 1.4.1 and later.
-enable_peer_stats
Activates the collection of Rx statistics and allocates memory for their storage. For
each connection with a specific UDP port on another machine, a separate record is kept
for each type of RPC (FetchFile, GetStatus, and so on) sent or received. To display or
otherwise access the records, use the Rx Monitoring API.
-enable_process_stats
Activates the collection of Rx statistics and allocates memory for their storage. A
separate record is kept for each type of RPC (FetchFile, GetStatus, and so on) sent or
received, aggregated over all connections to other machines. To display or otherwise
access the records, use the Rx Monitoring API.
-syslog [<loglevel]
Use syslog instead of the normal logging location for the fileserver process. If
provided, log messages are at <loglevel> instead of the default LOG_USER.
-mrafslogs
Use MR-AFS (Multi-Resident) style logging. This option is deprecated.
-saneacls
Offer the SANEACLS capability for the fileserver. This option is currently
unimplemented.
-help
Prints the online help for this command. All other valid options are ignored.
-vhandle-setaside <fds reserved for non-cache io>
Number of file handles set aside for I/O not in the cache. Defaults to 128.
-vhandle-max-cachesize <max open files>
Maximum number of available file handles.
-vhandle-initial-cachesize <initial open file cache>
Number of file handles set aside for I/O in the cache. Defaults to 128.
-vattachpar <number of volume attach threads>
The number of threads assigned to attach and detach volumes. The default is 1.
Warning: many of the I/O parallelism features of Demand-Attach Fileserver are turned
off when the number of volume attach threads is only 1.
This option is only meaningful for a file server built with pthreads support.
-m <min percentage spare in partition>
Specifies the percentage of each AFS server partition that the AIX version of the File
Server creates as a reserve. Specify an integer value between 0 and 30; the default is
8%. A value of 0 means that the partition can become completely full, which can have
serious negative consequences. This option is not supported on platforms other than
AIX.
-lock
Prevents any portion of the fileserver binary from being paged (swapped) out of memory
on a file server machine running the IRIX operating system. This option is not
supported on platforms other than IRIX.
-sync <always | delayed | onclose | never>
This option changes how hard the fileserver tries to ensure that data written to
volumes actually hits the physical disk.
Normally, when the fileserver writes to disk, the underlying filesystem or Operating
System may delay writes from actually going to disk, and reorder which writes hit the
disk first. So, during an unclean shutdown of the machine (if the power goes out, or
the machine crashes, etc), or if the physical disk backing store becomes unavailable,
file data may become lost that the server previously told clients was already
successfully written.
To try to mitigate this, the fileserver will try to "sync" file data to the physical
disk at numerous points during various I/O. However, this can result in significantly
reduced performance. Depending on the usage patterns, this may or may not be
acceptable. This option dictates specifically what the fileserver does when it wants
to perform a "sync".
There are several options; pass one of these as the argument to -sync. The default is
"delayed".
always
This causes a sync operation to always sync immediately and synchronously. This
is the slowest option that provides the greatest protection against data loss in
the event of a crash or backing store unavailability.
Note that this is still not a 100% guarantee that data will not be lost or
corrupted during a crash. The underlying filesystem itself may cause data to be
lost or corrupt in such a situation. And OpenAFS itself does not (yet) even
guarantee that all data is consistent at any point in time; so even if the
filesystem and OS do not buffer or reorder any writes, you are not guaranteed that
all data will be okay after a crash.
This option may be appropriate if you have reason to believe a server is prone to
data loss failures, such as if the server encounters frequent power failures or
connectivity issues with network attached storage. Or if the backend storage is
temporarily degraded in some way (for example, a battery on a caching controller
fails), it may make sense to temporarily use the "always" option until the
situation is fixed. Some servers may also allow for sync operations to occur very
quickly, such that the "always" option is not noticeably slower than any other
option. In such a case, there is no downside to specifying "always".
This was the only behavior allowed in OpenAFS releases prior to 1.4.5.
delayed
This causes a sync to do nothing immediately, but the sync will happen sometime in
the background, within approximately the next 10 seconds. This works by having a
separate thread that goes through all open file handles every 10 seconds, and it
syncs the ones that have been marked as needing a sync. File handles flagged for
sync may also get synced on volume detachment, according to the same behavior as
with the "onclose" option.
This option is currently not recommended, since in the past the code implementing
this option has caused rare data corruption during normal operation. However, it
is currently the default option to allow consistent behavior from previous OpenAFS
releases.
This was the only behavior allowed in OpenAFS releases starting from 1.4.5 up to
and including 1.6.2. It is the default starting in OpenAFS 1.6.3. This option will
be removed in a future version of OpenAFS, and the default behavior will likely
change to the "onclose" behavior.
onclose
This causes a sync to do nothing immediately, but causes the relevant file to be
flagged as potentially needing a sync. When a volume is detached, flagged volume
metadata files are synced, as well as data files that have been accessed recently.
Events that cause a volume to detach include: performing certain volume operations
(restore, salvage, offline, et al), detection of volume consistency errors, a
clean shutdown of the fileserver, or during DAFS "soft detachment".
Effectively this option is the same as "never" while a volume is attached and
actively being used, but if a volume is detached, there is an additional guarantee
for the data's consistency.
never
This causes all syncs to never do anything. This is the fastest option, with the
weakest guarantees for data consistency.
Depending on the underlying filesystem and Operating System, there may be
guarantees that any data written to disk will hit the physical media after a
certain amount of time. For example, Linux's pdflush process usually makes this
guarantee, and ext3 can make certain various consistency guarantees according to
the options given. ZFS on Solaris can also provide similar guarantees, as can
various other platforms and filesystems. Consult the documentation for your
platform if you are unsure.
Which option you choose is not an easy decision to make. Various developers and
experts sometimes disagree on which option is the most reasonable, and it may depend
on the specific scenario and workload involved. Some argue that the "always" option
does not provide significantly greater guarantees over any other option, whereas
others argue that choosing anything besides the "always" option allows for an
unacceptable risk of data loss. This may depend on your usage patterns, your hardware,
your platform and filesystem, and who you talk to about this topic.
-fs-state-dont-save
When present, fileserver state will not be saved during shutdown. Default is to save
state.
-fs-state-dont-restore
When present, fileserver state will not be restored during startup. Default is to
restore state on startup.
-fs-state-verify (none | save | restore | both)
This argument controls the behavior of the state verification mechanism. A value of
"none" turns off all verification. A value of "save" only performs the verification
steps prior to saving state to disk. A value of "restore" only performs the
verification steps after restoring state from disk. A value of "both" performs all
verifications steps both prior to save and following a restore.
The default is "both".
-vhashsize <size
The log(2) number of of volume hash buckets. Default is 8 (i.e., by default, there
are 2^8 = 256 volume hash buckets). The minimum that can be specified is 6 (64 hash
buckets). In OpenAFS 1.5.77 and earlier, the maximum that can be specified is 14
(16384 buckets). After 1.5.77, the maximum that can be specified is 28 (268435456
buckets).
-vlruthresh <minutes
The number of minutes of inactivity before a volume is eligible for soft detachment.
Default is 120 minutes.
-vlruinterval <seconds
The number of seconds between VLRU candidate queue scan. The default is 120 seconds.
-vlrumax <positive integer
The maximum number of volumes which can be soft detached in a single pass of the
scanner. Default is 8 volumes.
-unsafe-nosalvage
This option causes the fileserver to bypass the normal safety check when attaching
volumes that checks the inUse field in the volume header. With this option, volumes
that were in use at the time of an unclean shutdown will not be salvaged immediately
the next time they are accessed, and thus risk (possibly silent and/or irrevocable)
corruption. Volumes will still be salvaged when an internal inconsistency is detected
or other cases where a salvage would normally occur.
Due to the increased risk of data corruption, the use of this flag is strongly
discouraged. Only use it if you really know what you are doing.
EXAMPLES
The following bos create command creates a dafs process on the file server machine
"fs2.abc.com" that uses the large configuration size, and allows volumes to exceed their
quota by 10%. Type the command on a single line:
% bos create -server fs2.abc.com -instance dafs -type dafs \
-cmd "/usr/lib/openafs/dafileserver -pctspare 10 -L" \
/usr/lib/openafs/davolserver \
/usr/lib/openafs/salvageserver \
/usr/lib/openafs/dasalvager
TROUBLESHOOTING
Sending process signals to the File Server Process can change its behavior in the
following ways:
Process Signal OS Result
---------------------------------------------------------------------
File Server XCPU Unix Prints a list of client IP
Addresses.
File Server USR2 Windows Prints a list of client IP
Addresses.
File Server POLL HPUX Prints a list of client IP
Addresses.
Any server TSTP Any Increases Debug level by a power
of 5 -- 1,5,25,125, etc.
This has the same effect as the
-d XXX command-line option.
Any Server HUP Any Resets Debug level to 0
File Server TERM Any Run minor instrumentation over
the list of descriptors.
Other Servers TERM Any Causes the process to quit.
File Server QUIT Any Causes the File Server to Quit.
Bos Server knows this.
The basic metric of whether an AFS file server is doing well is the number of connections
waiting for a thread, which can be found by running the following command:
% rxdebug <server> | grep waiting_for | wc -l
Each line returned by "rxdebug" that contains the text "waiting_for" represents a
connection that's waiting for a file server thread.
If the blocked connection count is ever above 0, the server is having problems replying to
clients in a timely fashion. If it gets above 10, roughly, there will be noticeable
slowness by the user. The total number of connections is a mostly irrelevant number that
goes essentially monotonically for as long as the server has been running and then goes
back down to zero when it's restarted.
The most common cause of blocked connections rising on a server is some process somewhere
performing an abnormal number of accesses to that server and its volumes. If multiple
servers have a blocked connection count, the most likely explanation is that there is a
volume replicated between those servers that is absorbing an abnormally high access rate.
To get an access count on all the volumes on a server, run:
% vos listvol <server> -long
and save the output in a file. The results will look like a bunch of vos examine output
for each volume on the server. Look for lines like:
40065 accesses in the past day (i.e., vnode references)
and look for volumes with an abnormally high number of accesses. Anything over 10,000 is
fairly high, but some volumes like root.cell and other volumes close to the root of the
cell will have that many hits routinely. Anything over 100,000 is generally abnormally
high. The count resets about once a day.
Another approach that can be used to narrow the possibilities for a replicated volume,
when multiple servers are having trouble, is to find all replicated volumes for that
server. Run:
% vos listvldb -server <server>
where <server> is one of the servers having problems to refresh the VLDB cache, and then
run:
% vos listvldb -server <server> -part <partition>
to get a list of all volumes on that server and partition, including every other server
with replicas.
Once the volume causing the problem has been identified, the best way to deal with the
problem is to move that volume to another server with a low load or to stop any runaway
programs that are accessing that volume unnecessarily. Often the volume will be enough
information to tell what's going on.
If you still need additional information about who's hitting that server, sometimes you
can guess at that information from the failed callbacks in the FileLog log in /var/log/afs
on the server, or from the output of:
% /usr/afsws/etc/rxdebug <server> -rxstats
but the best way is to turn on debugging output from the file server. (Warning: This
generates a lot of output into FileLog on the AFS server.) To do this, log on to the AFS
server, find the PID of the fileserver process, and do:
kill -TSTP <pid>
where <pid> is the PID of the file server process. This will raise the debugging level so
that you'll start seeing what people are actually doing on the server. You can do this up
to three more times to get even more output if needed. To reset the debugging level back
to normal, use (The following command will NOT terminate the file server):
kill -HUP <pid>
The debugging setting on the File Server should be reset back to normal when debugging is
no longer needed. Otherwise, the AFS server may well fill its disks with debugging
output.
The lines of the debugging output that are most useful for debugging load problems are:
SAFS_FetchStatus, Fid = 2003828163.77154.82248, Host 171.64.15.76
SRXAFS_FetchData, Fid = 2003828163.77154.82248
(The example above is partly truncated to highlight the interesting information). The Fid
identifies the volume and inode within the volume; the volume is the first long number.
So, for example, this was:
% vos examine 2003828163
pubsw.matlab61 2003828163 RW 1040060 K On-line
afssvr5.Stanford.EDU /vicepa
RWrite 2003828163 ROnly 2003828164 Backup 2003828165
MaxQuota 3000000 K
Creation Mon Aug 6 16:40:55 2001
Last Update Tue Jul 30 19:00:25 2002
86181 accesses in the past day (i.e., vnode references)
RWrite: 2003828163 ROnly: 2003828164 Backup: 2003828165
number of sites -> 3
server afssvr5.Stanford.EDU partition /vicepa RW Site
server afssvr11.Stanford.EDU partition /vicepd RO Site
server afssvr5.Stanford.EDU partition /vicepa RO Site
and from the Host information one can tell what system is accessing that volume.
Note that the output of vos_examine(1) also includes the access count, so once the problem
has been identified, vos examine can be used to see if the access count is still
increasing. Also remember that you can run vos examine on the read-only replica (e.g.,
pubsw.matlab61.readonly) to see the access counts on the read-only replica on all of the
servers that it's located on.
PRIVILEGE REQUIRED
The issuer must be logged in as the superuser "root" on a file server machine to issue the
command at a command shell prompt. It is conventional instead to create and start the
process by issuing the bos create command.
SEE ALSO
BosConfig(5), FileLog(5), bos_create(8), bos_getlog(8), fs_setacl(1), msgget(2),
msgrcv(2), salvager(8), volserver(8), vos_examine(1)
COPYRIGHT
IBM Corporation 2000. <http://www.ibm.com/> All Rights Reserved.
This documentation is covered by the IBM Public License Version 1.0. It was converted
from HTML to POD by software written by Chas Williams and Russ Allbery, based on work by
Alf Wachsmann and Elizabeth Cassell.