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: 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

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
```
```
```output
  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
```
```
```output
  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