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Version: 3.1

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: xxxxxxxx-xxxx-xxxx-xxxx-f929bc658862
    	IP: X.X.X.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: xxxxxxxx-xxxx-xxxx-xxxx-70019d925a4a
    	Scheduler: none
    	Nodes: 3 node(s) with storage (3 online)
    	IP		ID					SchedulerNodeName	StorageNode	UseCapacity	Status	StorageStatus	Version		Kernel				OS
    	X.X.X.28	xxxxxxxx-xxxx-xxxx-xxxx-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)
    	X.X.X.240	xxxxxxxx-xxxx-xxxx-xxxx-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)
    	X.X.X.32	xxxxxxxx-xxxx-xxxx-xxxx-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
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