Single Node Ceph Recovery


Active Member
Dec 4, 2018
If I were running Ceph (testing, no crucial data on this cluster) with only a single node (pools set to replicate OSD instead of host). If the host OS were to fail, but all the Bluestore OSDs were fine, can I import those into a new cluster after reinstalling the host OS? Or is the data lost forever?
They are lost, as the MON DB is located on the OS disk.
The state of the cluster is written to that DB and that is always changing. If there is no crucial data on it, then why bother? ;)
Sorry for necroposting but what will happen if we improve ccloyd's question a bit:

First node is a ceph storage with 4 HDD's + some OS disk.
Second node is monitor only node with OS disk and no storage.

Question: can we somehow recover first node's OSD's if first node's OS disk will fail?
Question: can we somehow recover first node's OSD's if first node's OS disk will fail?
A Ceph cluster hast 3x MONs (quorum). If one fails, the others will still have that data. You can easily test this in a virtual setup.
So if first node fail with OS disk i just need standart steps to recover it?:
1. Remove from cluster
2. Change OS disk, reinstall system, configure
3. Add it back to cluster and recreate MON
4. MON will be synced from 2-nd node (MON only) and i could run old OSD's

Am i right?
Yes, that's it, in an rough outline.
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