Two questions regarding OSDs

[0x88e5]

Hello there! I hope everybody is doing fine! I've been working with Ceph + Proxmox for a while and I came to two questions regarding OSDs in Proxmox:

First: If I disconnect an OSD for whatever reason, for example pulled the physical storage unit associated with that very OSD, can I start the OSD again without going through the process of "Take it out, ensure it's down, destory..etc"?

Second: My Ceph setup has pools with 3/2 settings. I know that that means the cluster will still be functioning in case one OSD fails. But the question if two OSD failed what will happen to the cluster since only one OSD remained functioning?

Thanks in advance

 

[0x88e5]

Any replies..

 

[fiona]

Hi,
I'm not a Ceph expert, so please take my answers with a grain of salt.

Hello there! I hope everybody is doing fine! I've been working with Ceph + Proxmox for a while and I came to two questions regarding OSDs in Proxmox:

First: If I disconnect an OSD for whatever reason, for example pulled the physical storage unit associated with that very OSD, can I start the OSD again without going through the process of "Take it out, ensure it's down, destory..etc"?

If you don't take it out first, Ceph will not rebalance the data (which is bad as it decreases redundancy). Destroying the OSD is not strictly necessary, but it's not clean either, see here,

Second: My Ceph setup has pools with 3/2 settings. I know that that means the cluster will still be functioning in case one OSD fails. But the question if two OSD failed what will happen to the cluster since only one OSD remained functioning?

If you only have three OSDs, the cluster will be dead when two fail. You should always have at least three up and running. Note that you can create multiple OSDs per node to reduce the likelyhood of such failure.

Thanks in advance

 

[0x88e5]

Thanks