HTCACHECLEAN(8) htcacheclean HTCACHECLEAN(8)NAME
htcacheclean - Clean up the disk cache
SYNOPSIS
htcacheclean [ -D ] [ -v ] [ -t ] [ -r ] [ -n ] -ppath -llimit
htcacheclean [ -n ] [ -t ] [ -i ] -dinterval -ppath -llimit
SUMMARY
htcacheclean is used to keep the size of mod_disk_cache's storage within a certain limit. This tool can run either manually or in daemon
mode. When running in daemon mode, it sleeps in the background and checks the cache directories at regular intervals for cached content to
be removed. You can stop the daemon cleanly by sending it a TERM or INT signal.
OPTIONS -dinterval
Daemonize and repeat cache cleaning every interval minutes. This option is mutually exclusive with the -D, -v and -r options. To
shutdown the daemon cleanly, just send it a SIGTERM or SIGINT.
-D Do a dry run and don't delete anything. This option is mutually exclusive with the -d option.
-v Be verbose and print statistics. This option is mutually exclusive with the -d option.
-r Clean thoroughly. This assumes that the Apache web server is not running (otherwise you may get garbage in the cache). This option
is mutually exclusive with the -d option and implies the -t option.
-n Be nice. This causes slower processing in favour of other processes. htcacheclean will sleep from time to time so that (a) the disk
IO will be delayed and (b) the kernel can schedule other processes in the meantime.
-t Delete all empty directories. By default only cache files are removed, however with some configurations the large number of directo-
ries created may require attention. If your configuration requires a very large number of directories, to the point that inode or
file allocation table exhaustion may become an issue, use of this option is advised.
-ppath Specify path as the root directory of the disk cache. This should be the same value as specified with the CacheRoot directive.
-llimit
Specify limit as the total disk cache size limit. The value is expressed in bytes by default (or attaching B to the number). Attach
K for Kbytes or M for MBytes.
-i Be intelligent and run only when there was a modification of the disk cache. This option is only possible together with the -d
option.
EXIT STATUS
htcacheclean returns a zero status ("true") if all operations were successful, 1 otherwise.
Apache HTTP Server 2008-05-06 HTCACHECLEAN(8)
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vxcached(1M)vxcached(1M)NAME
vxcached - resize cache volumes when required
SYNOPSIS
/etc/vx/bin/vxcached [-v] [mail-address ...]
DESCRIPTION
The Veritas Volume Manager cache daemon, vxcached, is invoked by the VxVM kernel to monitor the cache objects that are used by space-opti-
mized snapshots. When usage of a cache volume by space-optimized snapshots reaches the high watermark level that has been set for the
cache, vxcached automatically grows the cache volume if this is required and configured.
The -v option enables the daemon in verbose mode. If no mail addresses are given as arguments, mail is sent to root.
If the autogrow feature has been enabled on a cache object, the values of the highwatermark, autogrowby and maxautogrow attributes for the
cache object determine the behavior of vxcached:
o When cache usage reaches the high watermark value, highwatermark, (default value is 90 percent), and the new required cache size would
not exceed the value of maxautogrow (default value is twice the size of the cache volume in blocks), vxcached grows the size of the
cache volume by the value of autogrowby (default value is 20% of the size of the cache volume in blocks).
o When cache usage reaches the high watermark value, and the new required cache size would exceed the value of maxautogrow, vxcached
deletes the oldest snapshot in the cache. If there are several snapshots with the same age, the largest of these is deleted.
If the autogrow feature has been disabled on a cache object:
o When cache usage reaches the high watermark value, vxcached deletes the oldest snapshot in the cache. If there are several snapshots
with the same age, the largest of these is deleted. If there is only a single snapshot, the snapshot is detached and marked as invalid.
The values of the highwatermark, autogrowby and maxautogrow attributes can be set when a cache object is created using vxmake. If neces-
sary, you can use the vxcache set command to change the values of these attributes for an existing cache.
NOTES
The vxcached daemon is started automatically if a license for the FastResync feature is already present on the system. If you add such a
license while VxVM is running, you can either start vxcached manually, or shut down and reboot the system.
Killing the vxcached process stops it from removing snapshots. The daemon can be prevented from being started by commenting out its entry
in the startup script, /sbin/init.d/vxvm-recover.
The vxcached daemon does not remove snapshots that are currently open, and it does not remove the last or only snapshot in the cache.
If the cache space becomes exhausted, the snapshot is detached. If this happens, the snapshot is unrecoverable and must be removed manu-
ally. Enabling the autogrow feature on the cache helps to avoid this situation occurring. However, for very small caches (of the order of
a few megabytes), it is possible for the cache to become exhausted before the system has time to respond and grow the cache. In such
cases, either increase the size of the cache manually, or reduce the value of highwatermark.
You can use the maxautogrow attribute to limit the maximum size to which a cache can grow. To estimate this size, consider how much the
contents of each source volume are likely to change between snapshot refreshes, and allow some additional space for contingency.
SEE ALSO vxcache(1M), vxintro(1M), vxmake(1M), vxsnap(1M)VxVM 5.0.31.1 24 Mar 2008 vxcached(1M)