raidz1 on SSDs? What to read?

[daemonix]

Hi,

Can you point me to some rtfm, or give me an overview, about the things I need to check when configuring a raid array with SSDs only? (I have total of 6 SSD but Ill probably use 5 and one keep as cold swap??).

Im new to truenas, I have done linux software raid (20 years ago maybe?) and I have a couple of synology 8bay boxes.

I have seen in random posts negative comments about SSD arrays and/or some tips but Im not sure I have the complete picture. Can someone give me an overview?

My current dataset is 11-ish TB (the one Im replacing) and not very high activity. I mostly push and pull things in bursts so I need the 10Gbe speed of the new system to make my work easier. The system will have 8x 8tb 870 drive so Im not sure if it makes sense to do one vdev now with 3 disks and keep the other 3 for another vdev 1 year later... I saying this as with truenas you cant expand the array with more drives (yes?) and I have read comments about ssds getting errors at a similar rate so all are dead together.. :S :S

Any ideas, help or RTFM will be appreciated...

Thanks

 

[sretalla]

Be aware that although SSDs have high IOPS as a general rule, a RAIDZ1 VDEV/pool will have the total (at least Write) IOPS of only one of the drives.

Your throughput will be better than 1 single drive, but IOPS will be limited to one.

If that's fine for you, no problem.

If your reason for using SSDs is for high IOPS, you need to think about Mirrors (and possibly an Optane SLOG if you're doing sync writes). Generally speaking that would mean you're doing block storage, so read this: https://www.truenas.com/community/threads/the-path-to-success-for-block-storage.81165/
Even if it's talking about HDDs, the theory is still relevant for sync writes.

 

[daemonix]

Be aware that although SSDs have high IOPS as a general rule, a RAIDZ1 VDEV/pool will have the total (at least Write) IOPS of only one of the drives.

Your throughput will be better than 1 single drive, but IOPS will be limited to one.

If that's fine for you, no problem.

If your reason for using SSDs is for high IOPS, you need to think about Mirrors (and possibly an Optane SLOG if you're doing sync writes). Generally speaking that would mean you're doing block storage, so read this: https://www.truenas.com/community/threads/the-path-to-success-for-block-storage.81165/
Even if it's talking about HDDs, the theory is still relevant for sync writes.

aha! I didnt know this technicality but even one drive is way more than my WD Red Pro drive I believe... My main goal was to be as close to 10Gbe as possible.
Additional plus was that I wouldnt worry about spinning disks.. (lower power consumption too :P)