Ceph node without any OSDs ?

[ozdjh]

Hi

I think this will work fine but thought I'd ask here before I buy another license to try it out. Can I have a node that is part of the ceph cluster but doesn't have any OSDs? I want to have a cluster node that is just a 'ceph client'. It would not run VMs. It'd just be used for rbd exports to local storage.

<background> Our current 'cloud platform' uses a similar concept to do backups (a dedicated node that is part of the storage network that only does backups). It's about the only part of the platform I like . The nodes running the VMs are dedicated to running vms, and the nodes setup for backups are dedicated to that. And the backups are "pull" backups, not "push" backups from the hypervisors, so if anything goes wrong you just get failed backups, not failed production hypervisors.

Anyway, it's something I'm going to investigate as part of our proxmox evaluation. So will ceph talk to a node that doesn't have any OSDs.


David
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[t.lamprecht]

Can I have a node that is part of the ceph cluster but doesn't have any OSDs?

Yes, totally fine and often done. You can also use a Node just as ceph-monitor with no OSDs, for bigger setups that's even somewhat recommended.

So will ceph talk to a node that doesn't have any OSDs.

Yes. The remaining nodes should install the ceph packages too, though, this matches the software versions over all of the cluster and makes management easier.

And the backups are "pull" backups, not "push" backups from the hypervisors, so if anything goes wrong you just get failed backups, not failed production hypervisors.

With ceph being able to add sosfisticated redundancy and reliability that may not even become an issue, but it can be still a good design to separate "compute" from "storage" nodes.

 

[ozdjh]

Thanks @t.lamprecht, I'll run this up in the next day or 2. For our purposes it's more about separating the "backup" node from the "compute & storage" nodes so that an issue with one doesn't impact on the other. Thanks for your feedback and the quick response.