Manpages

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]
[-admin-write]
[-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]
[-transarc-logs]
[-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]
[-offline-timeout <timeout in seconds>]
[-offline-shutdown-timeout <timeout in seconds>]
[-sync <sync behavior>]
[-logfile <log file] [-config <configuration path]

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 default values are:

Parameter (Argument) Small (-S) Medium Large (-L)
---------------------------------------------------------------------
Number of threads (-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:

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 -w argument, which is intended for use by the OpenAFS developers only. Changing it from its default values can result in unpredictable File Server behavior.

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 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.

-nobusy

This option slightly changes the error codes reported to clients when an unattached volume is accessed by a client during fileserver startup.

Normally, non-DAFS fileservers start accepting requests immediately on startup, but attachment of volumes can take a while. So if a client tries to access a volume that is not attached simply because the fileserver hasn’t attached it yet, that client will get an error. With the -nobusy option present, the fileserver will immediately respond with an error code that indicates the server is starting up. However, some older clients (before OpenAFS 1.0) don’t understand this error code, and may not function optimally. So the default behavior, without the -nobusy option, is to at first respond with a different error code that is understood by more clients, but is indistinguishable from other scenarios where the volume is busy and not attached for other reasons.

There is usually no reason to use this option under normal operation.

-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.

-admin-write

Allows write requests for members of system:administrators on the read-only fileserver in question. The "-admin-write" option has no effect when the "-readonly" is not specified.

-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.

-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.

-transarc-logs

Use Transarc style logging features. Rename the existing log file /var/log/openafs/FileLog to /var/log/openafs/FileLog.old when the fileserver is restarted. This option is provided for compatibility with older versions.

-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.

-offline-timeout <timeout in seconds>

Setting this option to N means that if any clients are reading from a volume when we want to offline that volume (for example, as part of releasing a volume), we will wait N seconds for the clients’ request to finish. If the clients’ requests have not finished, we will then interrupt the client requests and send an error to those clients, allowing the volume to go offline.

If a client is interrupted, from the client’s point of view, it will appear as if they had accessed the volume after it had gone offline. For RO volumes, this mean the client should fail-over to other valid RO sites for that volume. This option may speed up volume releases if volumes are being accessed by clients that have slow or unreliable network connections.

Setting this option to 0 means to interrupt clients immediately if a volume is waiting to go offline. Setting this option to "-1" means to wait forever for client requests to finish. The default value is "-1".

-offline-shutdown-timeout <timeout in seconds>

This option behaves similarly to -offline-timeout but applies to volumes that are going offline as part of the fileserver shutdown process. If the value specified is N, we will interrupt any clients reading from volumes after N seconds have passed since we first needed to wait for a volume to offline during the shutdown process.

Setting this option to 0 means to interrupt all clients reading from volumes immediately during the shutdown process. Setting this option to "-1" means to wait forever for client requests to finish during the shutdown process.

If -offline-timeout is specified, the default value of -offline-shutdown-timeout is the value specified for -offline-timeout. Otherwise, the default value is "-1".

-sync <always | onclose | none>

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), 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 "onclose".
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.

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 was the only behavior allowed in OpenAFS releases prior to 1.4.5.

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, volume metadata files flaged for synced are synced, as well as data files that have been accessed recently. Events that cause a volume to detach include: performing volume operations (dump, restore, clone, etc), 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.

After the removal of the "delayed" option after the OpenAFS 1.6 series, this option became the default.

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.

delayed

This option used to exist in OpenAFS 1.6, but was later removed due to issues encountered with data corruption during normal operation. Outside of the OpenAFS 1.6 series, it is not a valid option, and the fileserver will fail to start if you specify this (or any other unknown option). It caused syncs to occur in a background thread, executing every 10 seconds.

This was the only behavior allowed in OpenAFS releases starting from 1.4.5 up to and including 1.6.2. It was also the default for the 1.6 series starting in OpenAFS 1.6.3.

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 platform and filesystem, and who you talk to about this topic.

-logfile <log file>

Sets the file to use for server logging. If logfile is not specified and no other logging options are supplied, this will be /var/log/openafs/FileLog. Note that this option is intended for debugging and testing purposes. Changing the location of the log file from the command line may result in undesirable interactions with tools such as bos.

-vhashsize <size

The log(2) of the number 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).

-config <configuration directory>

Set the location of the configuration directory used to configure this service. In a typical configuration this will be /etc/openafs/server - this option allows the use of alternative configuration locations for testing purposes.

-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".

-vlrudisable

This option completely disables the VLRU mechanism, which means volumes will never "soft detach". The use of this option is only intended for debugging use or if you find a serious bug in the VLRU mechanism you wish to work around.

-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.example.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.example.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.