Second CEPH pool for SSD

[Senin]

Hi!

I'm currently using 3-node PVE cluster with CEPH pool based on HDD (80Tb total).
Now I added 2 SSDs to each node and want to create second separate pool (10Tb total).
I read https://pve.proxmox.com/pve-docs/chapter-pveceph.html#pve_ceph_device_classes but some things are not clear to me.

As I understand I need 2 crush rules - one for hdd class and second for ssd class.
And then I have to bind this rules to CEPH pools.
But what should I do with existing pool?

The documentation says
"If the pool already contains objects, these must be moved accordingly. Depending on your setup, this may introduce a big performance impact on your cluster. As an alternative, you can create a new pool and move disks separately."

So I'm not sure how I can do this on production environment.
Any help?

 

[gurubert]

ceph osd pool set $poolname crush_rule $rulename

will assign a rule to an existing pool. Ceph will then move all the PGs with their objects according to the new rule.

 

[Senin]

Thank you for quick answer

Are there any possible performance issues?

Anyway I think I should perform this on the weekend.

 

[aaron]

Are there any possible performance issues?

There will be a rebalance. If your cluster is already running at its performance limit, this might push it over to the point where you see performance issues. But if you are at that point, then it is high time to upgrade the cluster or reduce load, as it should be able to handle such situations. Otherwise, a recovery situation due to some failure might cause the same issues, and those are harder to plan

You can also change the rule of a pool in the web UI when you edit the pool.