Checking persistent write log cache status

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You can check the status of the Persistent Write Log (PWL) cache. The cache is used when an exclusive lock is acquired, and when the exclusive-lock is released, the persistent write log cache is closed. The cache status shows information about the cache size, location, type, and other cache-related information. Updates to the cache status are done when the cache is opened and closed.

Prerequisites

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  • A running IBM Storage Ceph cluster.

  • Root-level access to the monitor node.

  • A running process with PWL cache enabled.

Procedure

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  • View the PWL cache status:

    Syntax

    rbd status POOL_NAME/IMAGE_NAME

    Example

    [ceph: root@host01 /]# rbd status pool1/image1
Watchers:
        watcher=10.10.0.102:0/1061883624 client.25496 cookie=140338056493088
Persistent cache state:
        host: host02
        path: /mnt/nvme0/rbd-pwl.rbd.101e5824ad9a.pool
        size: 1 GiB
        mode: ssd
        stats_timestamp: Mon Apr 18 13:26:32 2022
        present: true   empty: false    clean: false
        allocated: 509 MiB
        cached: 501 MiB
        dirty: 338 MiB
        free: 515 MiB
        hits_full: 1450 / 61%
        hits_partial: 0 / 0%
        misses: 924
        hit_bytes: 192 MiB / 66%
        miss_bytes: 97 MiB