Ceph block.db on SSD mirror (md-raid, lvm mirror or ZFS mirror)

[herzkerl]

I want to set up a mirror consisting of two SSDs, to use that as a DB/WAL device for several (HDD) OSD's.

The system doesn't have a hardware RAID controller, so basically there's three options (I guess):

• md raid or ZFS mirror — but /dev/zd0 or /dev/md127 are not accepted by pveceph create
• LVM Mirror (didn't try that one yet)

While I understand that general consensus (from a few years back) would be not to do that, providing a mirror — as DB/WAL device only(!) — reduces the probability of those OSDs to fail, which means in such event, Ceph wouldn’t have to recover quite a few TB’s on slow HDD’s, as long as the second SSD still works.

What would be your recommendation here?

 

[Hqu]

Hey,

mdadm raid are not recommended in general use for Proxmox. LVM sounds like a better option then.

Short documentation about current state of ceph in PVE: https://pve.proxmox.com/pve-docs/pve-admin-guide.pdf (S.189 - Disks)

Best