sspcache command

Purpose

The ioscli sspcache command is used to manage caching in a Shared Storage Pool (SSP) cluster. You can use the sspcache command to enable or disable existing caches throughout the cluster. You can also use the sspcache command to resize the existing caches in the cluster.

Syntax

sspcache -enable -sp -size cachelvsize

sspcache -disable -sp

sspcache -resize -sp -size cachelvsize

sspcache -status

sspcache -statistics

Description

The ioscli sspcache command is an asynchronous command. Running it triggers a background process on each node to do the actual work of setting up the cache. Therefore, enabling, disabling, or resizing a cache through the sspcache command gives you the result immediately, but the actual enabling or removing of the caches on each node happens later, sometimes within the next 5 minutes.

Besides managing the state of caching, the -status flag provides access to information from across the cluster, about the state of SSP caching on all nodes in the cluster.

The -statistics flag provides local information about how the caches are performing on a local node. This includes all available caches, and not just those caches that are created for SSP caching.

Important: Information about setting up your systems
To use SSP caching, you must ensure that your cluster meets the following two criteria:
  • A cache pool is available on each node on which you want to enable SSP caching. You can create the cache pool from a flash storage disk, by using the cache_mgt command.
  • The cache pool must be sufficiently large for caching to be enabled. If the cache pool on a particular node is smaller than the requested cache disk size, caching is not enabled on that node.

Flags

Flag name Description
-enable Enables caching of the Shared Storage Pool (SSP).
-disable Disables caching of the SSP.
-resize Increases the requested cache size for an SSP object that already has local caching enabled.
Note: You cannot resize a cache to a smaller size than the current requested size.
-status Displays the status of SSP caching for all nodes in the cluster. The status indicates which SSP objects are being cached, as well as cache specific information for each SSP cache in the cluster.
-sp Specifies that the operation must be performed on the entire SSP.
-size Specifies the cache size in MB. To specify Gigabytes, follow the number with gb or GB or g or G.
-statistics
Displays caching statistics for all caches on a particular node.
Note: Statistics are provided for both SSP caches and non-SSP caches.
The output of caching statistics includes the following details:
Population Percent
Displays the percentage of cache that is full. Normally, the value of population percentage stays around 100%.
Hit Rate
Displays the number of times a query to the storage pool has overlapped with the cache. This information means that the cache is used instead of the storage pool for the data, improving performance.
Target Type
Specifies the type of object that is being cached. Currently, the target type can either be a storage pool, or a virtual disk.
Target ID
Acts as an identifier for whichever SSP object is being cached. If the SSP object is a virtual disk, no information is displayed in this field.

Exit Status

Use error messages to determine success or failure. The command always exits with the value 0.

Examples

  1. To enable SSP caching after the cluster is made and all the nodes are created, type the following command:
    sspcache -enable -sp -size 100
    The system displays the following output:
    (0) padmin @ your_hostname: /home/padmin
$ sspcache -enable -sp -size 100 
Action processed successfully.

Note: This is an asynchronous operation.
      Please use `sspcache -status` to verify that this operation has succeeded
      on all nodes in the cluster at a later time.

      (5-10 minutes is the maximum expected delay.)
    This command creates a 100 MB cache on every node that has a cache pool, with at least 100 MB of free space. The default unit of measurement is MB. However, you can also specify gb or GB or g or G, if you want to create a larger cache.
  2. To create a 1 GB cache on every node that has a cache pool, with at least 1 GB of free space, type the following command:
    sspcache -enable -sp -size 1GB
    Note: The default unit of measurement is MB. However, you can also specify gb or GB or g or G, if you want to create a larger cache.
    The system displays the following output:
    (0) padmin @ your_hostname: /home/padmin
$ sspcache -enable -sp -size 1GB
Action processed successfully.

Note: This is an asynchronous operation.
      Please use `sspcache -status` to verify that this operation has succeeded
      on all nodes in the cluster at a later time.

      (5-10 minutes is the maximum expected delay.)
  3. To view the status of caching in the cluster, type the following command:
    sspcache -status
    The system displays the following output:
    (0) padmin @ your_hostname: /home/padmin
$ sspcache -status

Pool Information:
   Pool Name: your_hostname
   Caching Status: ENABLED
   Cache Size: 100MB

Node Information:
   Node Name: your_hostname
   Node ID: aa332f648c0011e7800eae9d8c643702
   Cached Pool: your_storage_pool
   Caching LV: cmpart0
   Caching LV Size: 128MB
    Note that 128 MB is larger than the 100 MB requested. Based on the disk that is used in the cache pool, there might be a limitation on how the cache_mgt command can allocate size.
  4. To view the status in a case where you enabled caching, but none of the nodes picked it up yet, type the following command:
    sspcache -status
    The system displays the following output:
    (0) padmin @ your_hostname: /home/padmin
$ sspcache -status

Pool Information:
   Pool Name: your_hostname
   Caching Status: ENABLED
   Cache Size: 100MB

Node Information:
   No nodes are currently caching.

    This output is an example of asynchronicity.

  5. To disable SSP caching on all nodes throughout the cluster, type the following command:
    sspcache -disable -sp
    The system displays the following output:
    (0) padmin @ your_hostname: /home/padmin
$ sspcache -disable -sp
Action processed successfully.

Note: This is an asynchronous operation.
      Please use `sspcache -status` to verify that this operation has succeeded
      on all nodes in the cluster at a later time.

      (5-10 minutes is the maximum expected delay.)
  6. To expand your SSP cache disks size to 200 MB (provided your cache size was smaller than 200 MB earlier), type the following command:
    sspcache -resize -sp -size 200
    The system displays the following output:
    (0) padmin @ your_hostname: /home/padmin
$ sspcache -resize -sp -size 200
Action processed successfully.

Note: This is an asynchronous operation.
      Please use `sspcache -status` to verify that this operation has succeeded
      on all nodes in the cluster at a later time.

      (5-10 minutes is the maximum expected delay.)
  7. If you want to attempt to resize your cache to 10 MB (provided your cache size was larger than 10 MB earlier), type the following command:
    sspcache -resize -sp -size 10
    The system displays an error, as shown in the following output:
    (0) padmin @ your_hostname: /home/padmin
$ sspcache -resize -sp -size 10
Updated cache partition size must be greater than the current cache partition size.
  8. To view the caching statistics for all local caches, type the following command:
    sspcache -statistics
    Note: The output of this command also displays non-SSP caches.
    The system displays the following output:
    (0) padmin @ your_hostname: /home/padmin
$ sspcache -statistics

Caching Statistics for Local Node (your_hostname):

   Cache Name: cmpart0
   Size: 128 MB

      Target Info:

      Population Percent: 0%
      Hit Rate: 0
      Target Type: SSP Pool
      Target ID: 0000000009035CDF0000000059A42E7C
Parent topic: Virtual I/O Server and Integrated Virtualization Manager commands listed alphabetically
Parent topic: Shared storage pool commands


Last updated: Thu, February 06, 2020