Ceph Pool Size?

[vispa]

Hi,

I'm after a little help with Ceph pools as I can't fully understand the calculator.

I have four nodes, each node has x6 500Gb drives which are my OSD's.

I'm looking to be able to sustain two nodes failing.

What would be the recommended pool size & pg num?

Regards,

James

 

[Alwin]

Check out that post: https://forum.proxmox.com/threads/ceph-raw-usage-grows-by-itself.38395/#post-189842

Also two node failure will halt your cluster, as there are simply not enough hosts available for this (>=5). While the data may be still available, Ceph and PVE will go into read-only mode (or even reboot if HA activated). You need at least three Ceph monitor and PVE hosts for quorum. With two failing, you definitely loose quorum on PVE side (four votes -> down to two). If it hits two of the Ceph MONs (very likely) then your Ceph cluster will halt too.

The calculator has description for the keys you input below. And the calculation is described beneath the calculator.
https://ceph.com/pgcalc/

I'm after a little help with Ceph pools as I can't fully understand the calculator.

What part of the calculator do you not understand?

 

[vispa]

Hi Alwin,

Ok that explains it. I was thinking that I had the pool configured incorrrectly which was causing the cluster to fail.

So the answer is, I need a minimum of five nodes to sustain a two node failure.

Thanks for your help.

James

 

[jagan]

If you are looking for two nodes failure, you should have cluster with Min. 5 PVE nodes