Need some guidance setting up a new RAIDz3

[Fritzolio]

The more I read the more confused I become. :(

I have 14 2TB drives. I want to maximize space (storage efficiency). RAIDz3 is optimized for 5,7 and 11 drives. If I break the pool up into 2 striped vDevs of 7 drives each, efficiency takes a nose dive. What happens if I put all drives into one vDev? Is this not advised or would it be OK?

Thanks and please pardon my ignorance. :)

 

[danb35]

I want to maximize space (storage efficiency).

Then why are you planning on using RAIDZ3?

 

[Spearfoot]

The more I read the more confused I become. :(

I have 14 2TB drives. I want to maximize space (storage efficiency). RAIDz3 is optimized for 5,7 and 11 drives. If I break the pool up into 2 striped vDevs of 7 drives each, efficiency takes a nose dive. What happens if I put all drives into one vDev? Is this not advised or would it be OK?

Thanks and please pardon my ignorance. :)

There's no hard-and-fast rule against using something other than 5, 7, or 11 disks in a RAIDZ3 vdev, so go ahead and use that approach if you want to. You'll save a disk by only having 3 parity disks vs. using 4 parity disks in a pair of RAIDZ2 vdevs.

 

[Fritzolio]

Then why are you planning on using RAIDZ3?

Data protection, what else?

 

[Fritzolio]

There's no hard-and-fast rule against using something other than 5, 7, or 11 disks in a RAIDZ3 vdev, so go ahead and use that approach if you want to. You'll save a disk by only having 3 parity disks vs. using 4 parity disks in a pair of RAIDZ2 vdevs.

Thanks. :)

 

[cyberjock]

I did a 16 disk RAIDZ3. It performs great, but after a while the performance ends up taking a nosedive and the only fix is to destroy and recreate.
I'd do 2 vdevs with that many disks. You can thank me later when performance isn't shit. ;)

 

[Spearfoot]

I did a 16 disk RAIDZ3. It performs great, but after a while the performance ends up taking a nosedive and the only fix is to destroy and recreate.
I'd do 2 vdevs with that many disks. You can thank me later when performance isn't shit. ;)

Just curious, @cyberjock - how full was your pool when performance started to degrade?

 

[cyberjock]

It wasn't quite to 80%.
Trust me.. your iops are limited to that of a single disk since you have 1 vdev. So eventually the bottleneck is the roughly 100 iops you get, which is totally performance killing when you've got TBs and TBs of data, etc.

 

[Spearfoot]

Yeah. We don't know the OP's use case, but he seemed to be concerned about space efficiency. A single 14-disk RAIDZ3 vdev is pretty efficient, but sure ain't gonna give the performance of 7 mirrored pairs!

 

[cyberjock]

Sure, we don't don't the use case. The issue is that virtually any use case is going to expect a certain amount of iops for a given amount of storage used, which is why the really wide vdevs suck. It's also what made my server unusable even though I was the sole user of the server and I never did more than one thing on the server at any given time. Even trying to do simple task of simply streaming a video on the server while doing basic work with files would create stuttering on the video.

 

[Fritzolio]

Think I'm gonna play around with a couple of different configs and see which works the best. It's main use will be as a backup for my media and personal stuff. Maybe a Z3 is overkill for my needs. I have another box with 2 pools of 10 disks in RAID Z2 that have worked well for over a year now.

 

[cyberjock]

Think I'm gonna play around with a couple of different configs and see which works the best. It's main use will be as a backup for my media and personal stuff. Maybe a Z3 is overkill for my needs. I have another box with 2 pools of 10 disks in RAID Z2 that have worked well for over a year now.

I ditched my "too-wide" RAIDZ3 and switched to my 10 disk RAIDZ2 and been very happy every since. That was almost 2 years ago now.

 

[Fritzolio]

I need to save up for some 3 or 4 TB drives. 10 2TB ain't big enough. I agree, I have 2 10 disk pools, one witrh 3TB drives and one with 1 TB drives. They've both been flawless for about a year now. Think I'll stick with what I know works.