vxcache(1M)															       vxcache(1M)

NAME

       vxcache - administer the cache object for space-optimized snapshots

SYNOPSIS

       vxcache [-g diskgroup] att volume cacheobj

       vxcache [-g diskgroup] dis cachevol ...

       vxcache [options] [-g diskgroup] growcacheby cacheobj lengthchange [attribute ...]

       vxcache [options] [-g diskgroup] growcacheto cacheobj newlength [attribute ...]

       vxcache [-g diskgroup] listvol  cacheobj

       vxcache [-g diskgroup] set attribute=value cacheobj ...

       vxcache [options] [-g diskgroup] shrinkcacheby cacheobj lengthchange [attribute ...]

       vxcache [options] [-g diskgroup] shrinkcacheto cacheobj newlength [attribute ...]

       vxcache [-g diskgroup] start cacheobj ...

       vxcache [-g diskgroup] stat [cacheobj ...]

       vxcache [-f] [-g diskgroup] stop cacheobj...

DESCRIPTION

       The  vxcache  utility is used to administer a cache object that is associated with volumes that have one or more space-optimized snapshots.
       The cache object, cacheobj, and underlying cache volume, cachevol, may be shared between volumes in a disk group.

KEYWORDS

       att	 Attaches a volume as a cache volume to a cache object.  If a valid cache object exists but the original  cache  volume  has  been
		 removed, this operation may be used to attach a new volume as a cache volume to the cache object.

       dis	 Dissociates one or more cache volumes from their cache objects.

		 Note: First use the vxcache stop command to stop the cache objects.

       growcacheby
		 Grows the cache by the specified amount, lengthchange.

       growcacheto
		 Grows the cache to the specified length, newlength.

       listvol	 Prints  a  space-separated  list of space-optimized instant snapshots that have been created on the specified cache object.  This
		 list is sorted by the timestamp on the snapshot.  If two or more snapshots have the same timestamp, these snapshots are sorted in
		 order of decreasing size.

       set	 Sets  the  value  of an attribute for the specified cache objects.  Values may be set for the autogrow, autogrowby, highwatermark
		 and maxautogrow attributes.  See the vxcached(1M) manual page for a description of these attributes.

       shrinkcacheby
		 Shrinks the cache by the specified amount, lengthchange.

       shrinkcacheto
		 Shrinks the cache to the specified length, newlength.

       start	 Starts cache objects and rebuilds the in-core mapping.

       stat	 Prints space usage statistics for cache objects:

		 TOTAL	   Total size of the cache volume in megabytes that is available to cache data.  As a small amount of space is required to
			   hold cache object metadata, this value is always smaller than the total size of the cache volume.

		 USED	   Size of the cache that is in use in megabytes and as a percentage.

		 AVAIL	   Size of the cache that is available for use in megabytes and as a percentage.

		 SDCNT	   Number of subdisks that have been created on the cache object.

		 If no cache objects are specified, statistics are displayed for all cache objects in the disk group.

       stop	 Stops cache objects.

OPTIONS

       Note: The -d and -n options apply only to the growcacheby, growcacheto, shrinkcacheby and shrinkcacheto operations.

       -d defaults
		 Specifies  a file containing defaults for various attributes related to space allocation for growing and shrinking the cache.	If
		 not specified, this defaults to /etc/default/vxassist.

       -f	 Forces the stop operation if any snapshots have been created on a cache object.

       -g diskgroup
		 Specifies the disk group for the operation, either by disk group ID or by disk group name.  If this option is not specified,  the
		 default disk group is determined using the rules given in the vxdg(1M) manual page.

       -n	 Prevents the system defaults file being read.

Hardware-Specific Options
       Note: These options apply only to the growcacheby, growcacheto, shrinkcacheby and shrinkcacheto operations.

       Some environments provide guidelines to optimize VxVM's interaction with intelligent storage systems. If these guidelines are present, VxVM
       follows them when allocating space for volumes.

       The following options change the behavior of the growcacheby, growcacheto, shrinkcacheby and shrinkcacheto operations:

       -o override
		 Performs the specified vxcache task for the specified volume and ignores any storage-specific guidelines. Overriding  the  guide-
		 lines is not recommended as it can result in incompatible objects, or objects that cannot be administered by VxVM and any associ-
		 ated software that exploit storage-specific features.

       -o verify Verifies that the vxcache task for the specified volume can be performed without violating any storage-specific  guidelines,  but
		 does not commit or perform any task.  If any guidelines are violated, vxcache exits with an error message.

       Note: These options need a separate license. Without the license, vxcache ignores the specified option.

       Refer to the vendor-specific documentation for more information on how intelligent storage systems can interact with VxVM.

EXAMPLES

       Create and enable a 1GB mirrored cache with a region size of 32KB:

	      vxassist -g mydg make cachevol 1g layout=mirror init=active 
		  mydg16 mydg17
	      vxmake -g mydg cache cobjmydg cachevolname=cachevol 
		  regionsize=32k
	      vxcache -g mydg start cobjmydg

       Grow the cache volume, mydgcvol, that is associated with the cache object, mydgcobj, by 1GB:

	      vxcache -g mydg growcacheby mydgcobj 1g

       Change the value of the maxautogrow attribute to 2GB for a cache:

	      vxcache -g mydg set maxautogrow=2g mydgcobj

       Stop and restart the cache object, mydgcobj, which has entered the DETACHED state after a failed grow or shrink operation (the -f option to
       vxcache stop is required because snapshots exist on the cache object):

	      vxcache -f -g mydg stop mydgcobj
	      vxcache -g mydg start mydgcobj

       Stop the cache object, mydgcobj, and dissociate the cache volume, mydgcvol, from it:

	      vxcache -g mydg stop mydgcobj
	      vxcache -g mydg dis mydgcvol

NOTES

       The attributes that may be specified with the growcacheby, growcacheto, shrinkcacheby and shrinkcacheto keywords are the same  as  for  the
       vxassist command.  See the vxassist(1M) manual page for details.

       The vxcached daemon monitors the usage of cache objects.  See the vxcached(1M) manual page for details.

       The minimum size of a cache volume is approximately 10m(10MB) plus 1MB for each 256KB of the region size.

SEE ALSO

       vxassist(1M), vxcached(1M), vxintro(1M), vxmake(1M), vxsnap(1M), vxstat(1M)

VxVM 5.0.31.1							    24 Mar 2008 						       vxcache(1M)