Optane SSD RAID Performance With ZFS On Linux, EXT4, XFS, Btrfs, F2FS

[darkbasic]

This is how the Optane should perform on ZFS when properly tuned: http://www.linuxsystems.it/2018/05/o...t4-benchmarks/

[mattlach]

Hmm. I've been considering picking up a pair of these 280GB Optane 900p drives to use as my ZIL/Slog drives mirrored on my ZFS storage server.

[Drizzt321]

That's my understanding, but you said: "Please if you have 2 SSD don't use RAIDZ since those are meant for parity raids" -- So I was wondering what you're saying to do (rather than not to do).

You're familiar with RAID levels? Well 2 disks don't properly do parity protected RAID, e.g. RAID5/6. In ZFS terms, that'd be RAIDZ/RAIDZ2. So with 2 disks, RAIDZ, while technically able to run, is an inefficient and slower use of the available disks. Either mirror (RAID1) or stripe (RAID0) would be appropriate depending on your requirements, with most folks with mirror being better.

So any benchmarks being done with RAIDZ with only 2 disks is NOT a valid benchmark from the perspective of it actually being a configuration pretty much anyone would ever use in the real world.

[deusexmachina]

You're familiar with RAID levels? Well 2 disks don't properly do parity protected RAID, e.g. RAID5/6. In ZFS terms, that'd be RAIDZ/RAIDZ2. So with 2 disks, RAIDZ, while technically able to run, is an inefficient and slower use of the available disks. Either mirror (RAID1) or stripe (RAID0) would be appropriate depending on your requirements, with most folks with mirror being better.

So any benchmarks being done with RAIDZ with only 2 disks is NOT a valid benchmark from the perspective of it actually being a configuration pretty much anyone would ever use in the real world.

So there's no ZFS option for mirror (raid1)?

[Drizzt321]

So there's no ZFS option for mirror (raid1)?

Did you read my full reply? There is.

http://www.zfsbuild.com/2010/05/26/zfs-raid-levels/

[deusexmachina]

Did you read my full reply? There is.

http://www.zfsbuild.com/2010/05/26/zfs-raid-levels/

OK, so that's what I thought... Why wouldn't someone use mirrored vdevs and 2 disks? If you have two 500GB disks, you only need 500GB, and you want to prevent any data loss... Then you could use mirrored vdevs, right? I'm wondering about ZFS performance with that - and I don't see why it would be worse than ZFS on a single drive.

[Drizzt321]

OK, so that's what I thought... Why wouldn't someone use mirrored vdevs and 2 disks? If you have two 500GB disks, you only need 500GB, and you want to prevent any data loss... Then you could use mirrored vdevs, right? I'm wondering about ZFS performance with that - and I don't see why it would be worse than ZFS on a single drive.

Should actually be faster, at least for reads. I _think_ ZFS will read from both devices for different blocks, but not sure. I know with RAIDZ/2 it can't, which means you're at the performance of a single disk.

[deusexmachina]

Should actually be faster, at least for reads. I _think_ ZFS will read from both devices for different blocks, but not sure. I know with RAIDZ/2 it can't, which means you're at the performance of a single disk.

Right so with two SSDs and mirrored vdevs - either drive can die without losing information... And potentially mirrored vdevs increase performance, as you say, but I'm not sure. However mirrored vdev Optane drives is the interest here - so should be fast enough regardless.

[deusexmachina]

So is this still true with AMD systems w/ Optane on Linux? I thought there was some Intel-only (CPU) relationship for Optane... Confusing.

[AsuMagic]

So is this still true with AMD systems w/ Optane on Linux? I thought there was some Intel-only (CPU) relationship for Optane... Confusing.

I think the Intel-only thing is about allowing the memory controller to use Optane directly as main system memory - without having to deal with swap or whatever.