Checking for fragmentation

Check the fragmentation level of BlueStore OSDs while the BlueStore OSD process is either online or offline.

Before you begin

Before you begin, make sure that you have the following prerequisites in place:

A running IBM Storage Ceph cluster.
BlueStore OSDs.

Getting an online BlueStore fragmentation score

Procedure

Inspect a running BlueStore OSD process by getting either a simple or more detailed report.

Get a simple report.

ceph daemon OSD_ID bluestore allocator score block

For example,

[ceph: root@host01 /]# ceph daemon osd.123 bluestore allocator score block

Get a detailed report.

ceph daemon OSD_ID bluestore allocator dump block

For example,

[ceph: root@host01 /]# ceph daemon osd.123 bluestore allocator dump block

Getting an offline BlueStore fragmentation score

Procedure

Reshard to check the offline BlueStore OSD.

For more information about resharding, see Resharding the RocksDB database.

[root@host01 ~]# cephadm shell --name osd.ID

For example,

[root@host01 ~]# cephadm shell --name osd.2
Inferring fsid 110bad0a-bc57-11ee-8138-fa163eb9ffc2
Inferring config /var/lib/ceph/110bad0a-bc57-11ee-8138-fa163eb9ffc2/osd.2/config
Using ceph image with id `17334f841482` and tag `cp.stg.icr.io/cp/ibm-ceph/ceph-9-rhel9:7-22/ibm-ceph@sha256:09fc3e5baf198614d70669a106eb87dbebee16d4e91484375778d4adbccadacd

Inspect a non-running BlueStore OSD process.

Inspect a running BlueStore OSD process by getting either a simple or more detailed report.

Get a simple report.

ceph-bluestore-tool --path PATH_TO_OSD_DATA_DIRECTORY --allocator block free-score

For example,

[root@host01 /]# ceph-bluestore-tool --path /var/lib/ceph/osd/ceph-123 --allocator block free-score

Get a detailed report.

ceph-bluestore-tool --path PATH_TO_OSD_DATA_DIRECTORY --allocator block free-dump
block:
{
    "fragmentation_rating": 0.018290238194701977
}

For example,

[root@host01 /]# ceph-bluestore-tool --path /var/lib/ceph/osd/ceph-123 --allocator block free-dump
block:
{
    "capacity": 21470642176,
    "alloc_unit": 4096,
    "alloc_type": "hybrid",
    "alloc_name": "block",
    "extents": [
        {
            "offset": "0x370000",
            "length": "0x20000"
        },
        {
            "offset": "0x3a0000",
            "length": "0x10000"
        },
        {
            "offset": "0x3f0000",
            "length": "0x20000"
        },
        {
            "offset": "0x460000",
            "length": "0x10000"
        },