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 guidelines is not recommended as it can result in incompatible objects, or objects that cannot be administered by VxVM and any associated 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 \0   mydg16 mydg17
vxmake -g mydg cache cobjmydg cachevolname=cachevol \0   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
To grow the cache volume using Solid State Devices (SSD) storage, use the following command:
vxcache -g mydg growcacheby mydgcobj 1g alloc=mediatype:ssd
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.

-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.

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