Question regarding minimal count of disks by using 3 nodes with ceph cluster

[Alexander Marek]

Hello all,

we are going to start with our ceph cluster soon.
in the beginning we will only use 3 nodes (we will expand system later with more nodes).
if we only use 2 disks per node for ceph your documentation tells that this is not good practice - so it would be a possibility to use 4 disks per node instead of 2 -"https://pve.proxmox.com/pve-docs/chapter-pveceph.html" - We recommend a Ceph cluster size, starting with 12 OSDs, distributed evenly among your, at least three nodes (4 OSDs on each node)..

Could you plase tell us in detail which kind of issues could occur if we only use 2 disks per node because it would take some months untill we would add more nodes?

BR, Alex

 

[Alwin]

About only 2 disks per node: It limits throughput and the amount of disk usage you shouldn't overstep quite a bit. You can find more about it in the Precondition section of our pve docs: https://pve.proxmox.com/pve-docs/pve-admin-guide.html#chapter_pveceph

Have look at our Ceph benchmark paper.
https://forum.proxmox.com/threads/proxmox-ve-ceph-benchmark-2018-02.41761/

 

[Alexander Marek]

Thank you Alwin!