Version: 3.1

Flush a pool's cache

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:

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

Enter the pxctl service pool cache status command with the ID of your storage pool:

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

Flush a pool's cache

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.

Enter the pxctl service pool cache flush command, specifying the <pool_id> of the pool you want to flush the cache of:

pxctl service pool cache flush <pool_id>

Depending on how many dirty blocks are in the cache, the operation will either run immediately, or in the background:
- The following example runs immediately and flushes the cache on pool 0:
```
pxctl service pool cache flush 0
```
```
Pool 0 has completed flush successfully
```
- The following example runs in the background and flushes the cache on pool 0:
```
pxctl service pool cache flush 0
```
```
Pool 0 flush cache initiated(has 12 dirty blocks)
```
  You can check the status of a background cache flush operation by entering the pxctl service pool cache flush command with the pool ID and the -o status flag:
```
pxctl service pool cache flush 0 -o status
```
```
Pool 0 has completed flush successfully
```

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.

Prerequisites​

Flush a pool's cache​

Prerequisites

Flush a pool's cache