New PBS, multiple drives, filesystem question

[Ramphex]

I'm setting up my first PBS and I have several SSD/HDD options I can use. I am curious on what would be the best choice of filesystems for each and whether ext4 is recommended for the OS drive and ZFS for the storage drives. I'm installing it on bare metal.

1x 240GB SSD - thinking OS drive... does it matter whether it's ext4 or xfs?
1x 1TB SSD - thinking special device
2x 8TB NAS HDDs - thinking storage drives in raid1 with the above-mentioned special device

Any recommendations on this setup are appreciated.

 

[Ramphex]

The server only supports 4 drives. Should I bother with 1 SSD special device or just use the 2 HDDs in ZFS mirror?

 

[UdoB]

The server only supports 4 drives. Should I bother with 1 SSD special device or just use the 2 HDDs in ZFS mirror?

Yes, that's a problem. I am fairly sure you won't get happy with only rotating rust.

First it will work. But on the long run - when the PBS gets filled - directory traversal will get so slow that a simple listing of the backups already fails. And overall everything is very slow then.

Been there, done that --> personally I just would not do that (again).

To counter-fight that behavior the idea with the Special Device is the way to go. Which leads to your hardware restrictions as the Special Device should really have the same redundancy level as the data part. It should be mirrored in this case.

The following is possibly not feasible through the normal installer, I just don't know. But I would try to use partitions to

• install the OS on only ~100 GB in a mirror. (Personally I use ZFS exclusively, others may be okay.)
• after installation create the data pool form the two HDDs
• now manually create a second partition on the SSDs with ~100 GB and add these two as the mentioned Special Device, also mirrored of course. Below one percent of capacity is required, iirc. Check this assumption somewhere else.

The remainder of that 1 TB SSD is not used in this approach. Oh, and the SSDs should be "Enterprise SSDs", as usual in the context of ZFS.

Good luck - and your mileage may vary!