TrueNAS - special meta data

[brocade351]

Hello, I wasn’t sure where to put this so here it goes. I watched one of your videos (recommendation from Lawrence systems: ZFS Metadata: Special Device And You!. I just setup a pool in TrueNAS that has a mirror 2TB SDD and then a MIRROR 1TB NVME special. I’m not sure the performance boost I’ll get considering it’s all SSD. I believe I found the option that you mention in your video. I plan to use this pool as a mix of zvols and datasets. The zvols will be for VM storage that I’m running on XCP-ng.

I believe I found the setting that you’re referring too in the video. It looks like it defaults to zero. The big poster is blocking it.

What do I need to figure out to make the best selection for a pool that contains VM data / datasets of general cloud files, etc. ?

[ThisMightBeAFish]

@brocade351

I just setup a pool in TrueNAS that has a mirror 2TB SDD and then a MIRROR 1TB NVME special. I’m not sure the performance boost I’ll get considering it’s all SSD.

You speed up metadata reads and writes. But a SSD mirror is already pretty good at that.

@brocade351

What do I need to figure out to make the best selection for a pool that contains VM data / datasets of general cloud files, etc. ?

Leave it at zero. The blue rectangle explains it pretty well.

You could use a PLP SSD as SLOG, if you want faster sync writes.

[PapaGigas]

@ThisMightBeAFish

You speed up metadata reads and writes. But a SSD mirror is already pretty good at that.

I think that this makes more sense for cacheless SSDs … using the NVMe for metadata/small blocks.

Best regards,
PapaGigas

[brocade351]

@ThisMightBeAFish

Leave it at zero. The blue rectangle explains it pretty well.

So, if i make this setting above 0 then files that take up blocks that are less than this size will be stored on my special disk.

@PapaGigas

I think that this makes more sense for cacheless SSDs … using the NVMe for metadata/small blocks.

Yeah, I mean that’s what I was thinking. I’m really just playing around and trying to learn.

What do you think my best configuration is for my current setup?

2x nvme 1TB and 2x SSD 2TB. I do plan to do sync writes for my VMs.

Should I do a RAIDZ1 with 1x NVME 1TB 2x SSD 2TB then keep the 1x nvme as a LOG?

[PapaGigas]

@brocade351

What do you think my best configuration is for my current setup?

I would create 2 pools, one for the system/apps/instances using the NVMe mirror, and another one for data/media/etc using the SSD mirror!

@brocade351

Should I do a RAIDZ1 with 1x NVME 1TB 2x SSD 2TB then keep the 1x nvme as a LOG?

That’s not possible, you need at least 3 identical disks for raidz1!

Best regards,
PapaGigas