Ceph OSD Journal on USB3.0 SSD?

[troycarpenter]

I built a ceph cluster earlier this year for one of my Proxmox clusters and it has been working just fine. I had enough drive slots in each storage node to include a dedicated SSD for the OSD journals and that cluster is working fine in terms of performance.

On a second cluster, I only had four drive slots in each of the storage nodes, one with the system drive and three OSDs. I thought putting the journal on the same drive as the OSD would be sufficient, but I believe now I underestimated the value of that SSD Journal drive in relation to performance. Since I'm out of internal drive slots in the storage servers, I have two options...I can either put an SSD in as the system drive and share with the journals (not recommended, I've read), or add the SSD drive as an external drive on a USB3.0 port.

Any thoughts on using an external USB3.0 SSD as the journal drive for the OSDs? I do understand the risk of the drives accidentally being disconnected, but that is a risk I'm willing to take right now.

Update: I've looked and the server has an internal USB3.0 port, so with a USB3.0 to SSD cable (around $8), I can secure the drive internal and avoid the accidental disconnection scenario.

 

[udo]

Hi,
I havn't testet usb3.0 drives but if I look at normal usb-drives behaviar on linux I would guess it's an really bad idea.

Do you don't have an internal sata-port (cdrom)?

Udo

 

[PigLover]

You'd really not enjoy running the journal on USB3

If you have an extra PCIe x4 (or larger) slot you could do much better with an M.2 NVMe SSD. Almost any would do better than the USB3 journal - but you could get some that are REALLY good. Fit it into the slot with a simple M.2 PCIe adapter card. As long as you are only using one M.2 drive the cards are cheap because they are just nearly-passive electrical adapters for for the connector.

Something like this: https://www.ebay.com/itm/M-2-NGFF-N...d=253177525430&_trksid=p2047675.c100011.m1850