Manually flush SSD cache

This article describes the following topics

• Ceph pool has reach the full ratio at ~=60%, by default it will automatically flush the data into HDD pool.
• But, in some production case, the incoming data/IO and the process of flushing data are stacked togather; It will cause a loop at 60% flushing data and accepting incoming data.
• It will create a consistent IOPS for a long period, So we must manually flush the Data with command.

Connect to a Controller

ssh [email protected]

Check the cache usage - ceph df

# ceph df
GLOBAL:
    SIZE        AVAIL       RAW USED     %RAW USED
    96.0TiB     73.0TiB      23.1TiB         24.02
POOLS:
    NAME                          ID     USED        %USED     MAX AVAIL     OBJECTS
    cachepool                     16      606GiB     60.18       1.00TiB      301519

Flush cache command

rados -p cachepool cache-flush-evict-all