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Where to find docs

The official Ceph documentation is located on

It is strongly advised to use the documentation for the version being used.

Critical medium error

The block device sdf has errors. You can see this in the kernel ring buffer, for example.

$ sudo dmesg
[14062414.575715] sd 14:0:5:0: [sdf] tag#2120 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_OK cmd_age=1s
[14062414.575722] sd 14:0:5:0: [sdf] tag#2120 Sense Key : Medium Error [current] [descriptor]
[14062414.575725] sd 14:0:5:0: [sdf] tag#2120 Add. Sense: Unrecovered read error
[14062414.575728] sd 14:0:5:0: [sdf] tag#2120 CDB: Read(16) 88 00 00 00 00 01 09 7c d9 50 00 00 00 80 00 00
[14062414.575730] critical medium error, dev sdf, sector 4454144360 op 0x0:(READ) flags 0x0 phys_seg 13 prio class 2

It may also be displayed in the health details of Ceph.

$ ceph -s
Too many repaired reads on 1 OSDs

$ ceph health detail
HEALTH_WARN Too many repaired reads on 1 OSDs
[WRN] OSD_TOO_MANY_REPAIRS: Too many repaired reads on 1 OSDs
osd.17 had 13 reads repaire

In this case the block device sdf is in the storage node sto1001. The OSD assigned to this block device can be determined.

$ ceph device ls | grep 'sto1001:sdf'
SEAGATE_ST16000NM004J_ZR604ZDZ0000C210PWE9 sto1001:sdf osd.17

If you only know the OSD ID, you can also determine the associated block device and the storage node.

$ ceph device ls | grep osd.17
SEAGATE_ST16000NM004J_ZR604ZDZ0000C210PWE9 sto1001:sdf osd.17

The broken OSD can be removed from the Ceph cluster. The Ceph cluster is then rebalanced. This can take some time and cause a high level of activity on the Ceph cluster.

$ ceph osd out osd.17
marked out osd.17.

On the storage node disable the OSD service for the OSD.

$ sudo systemctl stop ceph-osd@17.service