Ceph DB/WAL on SSD

[naltalef]

Hello.
I'm planning to install PVE on servers that have one SSD and six disks. The idea is to configure Ceph OSDs in each disk and dedicate the SSD to the DB/WAL.
When doing this configuration from the GUI, it doesn't seem to allow you to put both the DB and WAL on the SSD, but only one.
However, using the CLI, I understand that it's possible (I haven't tested it). Is this correct?
If you can't actually put both the DB and WAL on the SSD, which would be preferable?
Thank you very much.
Best regards.
Norberto

 

[SteveITS]

see https://pve.proxmox.com/wiki/Deploy_Hyper-Converged_Ceph_Cluster#pve_ceph_osds
"The WAL is placed with the DB, if not specified separately"

IIRC the default space usage is 10% (?) of the OSD size but you can adjust.

Side note: the SSD is a single point of failure for all 6 HDDs.

 

[naltalef]

see https://pve.proxmox.com/wiki/Deploy_Hyper-Converged_Ceph_Cluster#pve_ceph_osds
"The WAL is placed with the DB, if not specified separately"

IIRC the default space usage is 10% (?) of the OSD size but you can adjust.

Perfect. Understood

Side note: the SSD is a single point of failure for all 6 HDDs.

Wow. Sounds logical, but worrying.
I don't think it's a good idea to use it then. I'll leave it as local storage.

Many thanks for your help

 

[ness1602]

In the earlier days ,usually it was recommended 1 ssd or nvme onto 4 hdds for wal.

 

[naltalef]

In the earlier days ,usually it was recommended 1 ssd or nvme onto 4 hdds for wal.

Thanks for your response. Okay. In this case, it would be an SSD for six HDDs.
The problem is that I can't currently modify the existing hardware in each server.
That is, a 750 GB SSD and six 2.2 TB drives.
And I'm concerned about SPOF using one SSD with multiple drives.
I understand that the SSD isn't likely to fail, but if it does, I'll lose the entire Ceph node.