How to find which disk is used by an rbd

[RobFantini]

Hello
I have a disk which has an issue. per zabbix:
rbd15 : Disk read/write request responses are too high (read > 20 ms for 15m or write > 20 ms for 15m)

I spent an hour trying to find which disk has the issue. the regular cli tools I use , and could not find it.

so I checked dmsg and can see that rbd15 is used or created during pct backups:

dmesg|grep rbd15|less   #  Note this are from PCT backups.  not kvm.
[Wed Jan 22 02:00:02 2025] rbd: rbd15: capacity 17179869184 features 0x3d
[Wed Jan 22 02:00:02 2025] EXT4-fs (rbd15): write access unavailable, skipping orphan cleanup
[Wed Jan 22 02:00:02 2025] EXT4-fs (rbd15): mounted filesystem 19d9df32-3feb-4e8c-8af4-e0ce8002ecfe ro without journal. Quota mode: none.
[Wed Jan 22 02:01:02 2025] EXT4-fs (rbd15): unmounting filesystem 19d9df32-3feb-4e8c-8af4-e0ce8002ecfe.

So while doing a backup of a pct, i looked for the ext4 mounted file system and did not see it.

Question - how can I find out which physical disk is used by rbd15

 

[cheiss]

Hi,

rbd means it is a RADOS block device, i.e. stored in a Ceph cluster. This means it might (or might not) be a problem with your Ceph cluster, not a particular, single disk. The performance of a Ceph cluster has many variables.

Also, are these alerting rules appropriate for your expected performance from Ceph? As Ceph and local disks exhibit different characteristics, obviously.