Enable pool caching

Prerequisites

Before you can enable pool caching, you must have a storage pool with caching configured but currently disabled.

You can use the following commands to check if caching is disabled:

1. Run the pxctl status command the get the id of your pool:

   pxctl status

   Status: PX is operational
   License: Trial (expires in 29 days)
   Node ID: abb4723e-efa3-432d-ad27-f929bc658862
       IP: 70.0.79.28
       Local Storage Pool: 1 pool
       POOL    IO_PRIORITY RAID_LEVEL  USABLE  USED    STATUS  ZONE    REGION
       0   HIGH        raid0       128 GiB 8.4 GiB Online  default default
       Local Storage Devices: 2 devices
       Device  Path        Media Type      Size        Last-Scan
       0:0 /dev/sdf    STORAGE_MEDIUM_MAGNETIC 128 GiB     22 Sep 19 14:48 UTC
       total           -           128 GiB
       Cache Devices:
       Device  Path        Media Type      Size        Last-Scan
       0:1 /dev/sdc    STORAGE_MEDIUM_SSD  70 GiB      22 Sep 19 14:48 UTC
   Cluster Summary
       Cluster ID: doc-cluster-caching-2.2.0
       Cluster UUID: e5d79039-1333-4ac9-adf4-70019d925a4a
       Scheduler: none
       Nodes: 3 node(s) with storage (3 online)
       IP      ID                  SchedulerNodeName   StorageNode UseCapacity Status  StorageStatus   Version     Kernel              OS
       70.0.79.28  abb4723e-efa3-432d-ad27-f929bc658862    N/A         Yes     8.4 GiB 128 GiB     Online  Up (This node)  2.2.0.0-328a043 4.20.13-1.el7.elrepo.x86_64 CentOS Linux 7 (Core)
       70.0.78.240 9ddf713b-0dbc-4e7b-bd6e-2ae648891072    N/A         Yes     8.4 GiB 128 GiB     Online  Up      2.2.0.0-328a043 4.20.13-1.el7.elrepo.x86_64 CentOS Linux 7 (Core)
       70.0.79.32  0e466c6a-fef0-4752-b133-9bf257e9973a    N/A         Yes     8.4 GiB 128 GiB     Online  Up      2.2.0.0-328a043 4.20.13-1.el7.elrepo.x86_64 CentOS Linux 7 (Core)
   Global Storage Pool
       Total Used      :  25 GiB
       Total Capacity  :  384 GiB

2. Run the pxctl service pool cache status command with the id of your storage pool as a parameter:

   pxctl service pool cache status 0

   PX Cache Configuration and Status:
   Pool ID:  0
       Enabled:  false
       Members:  [/dev/sdc]
       TotalBlocks: 0
       UsedBlocks: 0
       DirtyBlocks: 0
       ReadHits: 0
       ReadMisses: 0
       WriteHits: 0
       WriteMisses: 0
       BlockSize: 1048576
       Mode: writeback
       Policy: smq
       Tunables: migration_threshold=20480

Enable pool caching

1. Enter pool maintenance mode:

   pxctl service pool maintenance --enter

   Pool transition operation will restart PX.
   Are you sure you want to proceed ? (Y/N): Y
   Pool transition request submitted.

2. Enter the pxctl service pool cache enable command, specifying the <pool_id> of the pool you want to disable caching for:

   pxctl service pool cache enable <pool_id>

   The following example enables caching for a pool with an ID of 0:

   pxctl service pool cache enable 0

   Pool 0 attached cache successfully

3. Exit pool maintenance mode:

   pxctl service pool maintenance --exit

   Pool transition operation will restart PX.
   Are you sure you want to proceed ? (Y/N): Y
   Pool transition request submitted.

4. At this point you can run the pxctl service pool cache status command to see if caching is enabled:

   PX Cache Configuration and Status:
   Pool ID:  0
       Enabled:  true
       Members:  [/dev/sdc]
       TotalBlocks: 71660
       UsedBlocks: 10
       DirtyBlocks: 6
       ReadHits: 13
       ReadMisses: 10
       WriteHits: 14
       WriteMisses: 8
       BlockSize: 1048576
       Mode: writeback
       Policy: smq
       Tunables: migration_threshold=20480