2 disk stripe with 2 additional HDDs for a RAIDZ1

[echelon5]

Hi. I'm running FreeNAS with:

• 2 x 4 TB WD RED mirrored
• 2 x 8 TB WD RED mirrored

I was thinking whether I'm making the most out of my setup.

Usecase:

• home setup, so uptime and resiliancy isn't my utmost concern
• Running 5 small VMs on a proxmox host with SSD. The VMs use the NAS only as a file storage. I.e. Owncloud runs on proxmox and files from FreeNAS are mounted through CIFS.
• Storing some movies and files that aren't accessed very frequently (torrenting). I'll watch a maximum of 2 movies at the same time from the NAS.

Right now I have 12 TB raw, but I was thinking about striping the 2 x 4TB and putting them all in a RAIDZ1 config, for that extra 4 TB raw space. I assume I wouldn't notice the slowdown considering the usecase. I'd loose the pool if 1 x 4 TB + 1 x 8 TB fails right? I also keep regular backups with the 3-2-1 strategy.

Now would be a good time to do this, while I can still backup to external HDDs to rebuild the pool. Is there any major downside to a setup like this? Is it doable? Can I do it from the GUI without the CLI?

Thanks!

 

[nojohnny101]

Some clarifications:
- do you currently have the 2 mirrors in the same pool or separate pools?

If you don't mind the downtime and understand the risks (the higher probability of one of your 8tb drives failing during a resilver) then raidz1 might make sense in your situation.

You're really killing yourself though by having drives of such varied sizes. Could you swing purchasing 2 more 8tb?

If you put all drives into a raidz1 then you cannot survive more than one of any drive failing.

 

[echelon5]

Some clarifications:
- do you currently have the 2 mirrors in the same pool or separate pools?

If you don't mind the downtime and understand the risks (the higher probability of one of your 8tb drives failing during a resilver) then raidz1 might make sense in your situation.

You're really killing yourself though by having drives of such varied sizes. Could you swing purchasing 2 more 8tb?

Each mirror is a separate pool. zpool status lists 2 pools.

The 2 x 8TB are relatively new and I can't afford 2 more. Moreover, I don't need that much space ATM, so it doesn't make financial sense to buy 2 more. By the time I'll need more space, they'll probably be half the price. Basically I'm using almost 4 TB now total, but I was considering switching to RAIDZ1 while I have enough external drives to backup and migrate the pools.

If you put all drives into a raidz1 then you cannot survive more than one of any drive failing.

Wouldn't I survive if both 4 TB failed? That's how I understood RAIDZ1: I'd have 3 vdevs out of which 1 vdev is the 2 x 4 TB striped. If 1 x 4 TB fails, the entire vdev fails, so I have to rebuild it by replacing the faulty drive. If 1 x 8 TB fails while I'm rebuilding the stripe vdev, the whole pool is gone.

 

[gpsguy]

You can't stripe the 2x4TB drives and then try to use it as a "disk" and then create a RAIDz1 array with the other two 8TB drives. You can't nest vdev's with ZFS.

 

[echelon5]

You can't stripe the 2x4TB drives and then try to use it as a "disk" and then create a RAIDz1 array with the other two 8TB drives. You can't nest vdev's with ZFS.

Damn. I saw this forum post and I thought it was possible.

 

[snaptec]

You could make a raidz1 out of 2x 8tb and 1x 4tb giving you about 8TB in total.
When space gets less replace the 4tb with a 8tb and you have got about 16tb space.
But I really don't suggest raidz1 with 8tb hdds.

use raidz2 up to 4tb and everything bigger raidz3.
As downtime is no problem and you have backups even raidz2 would be ok I think.


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[gpsguy]

From my read on that thread paleoN (who used to an active member) thought the OP was trying to create striped mirrors / which is allowable. The last poster explained the difference between striped mirrors and mirrored stripes, but didn't point out that you can't do that with FreeNAS.

Search the forum for Cybeejock's guide for an understanding of what you can do with vdev's.

 

[echelon5]

From my read on that thread paleoN (who used to an active member) thought the OP was trying to create striped mirrors / which is allowable. The last poster explained the difference between striped mirrors and mirrored stripes, but didn't point out that you can't do that with FreeNAS.

Search the forum for Cybeejock's guide for an understanding of what you can do with vdev's.

Yeah I went through his guide. I suspected it's a stretch, that's why I asked before trying anything :).

@snaptec

That setup sounds too complicated. It'll probably be a couple of years since I need more space and I'll probably buy a new unit and keep this one as a backup since it's limited to 4 bays.

Thanks all!

 

[gpsguy]

I think snaptec was focused on your desire to create a RAIDz1 array and didn't realize what you were proposing to do. At the moment your two mirrored vdev's offer the best configuration given the difference in sizes.

 

[echelon5]

I didn't know raidz1 can be created with disks of different sizes. His proposal would be interesting if I planned to upgrade my storage soon and use a 4tb drive as a placeholder (if I understood correctly). I gave it some thought but it's not worth it at the moment.

 

[Stux]

pity you didn't buy 4 4TB drives instead if two 8s

Then you could use 6x4TB Z2 and have 16TB usable.

 

[gpsguy]

Yeah, you can create the array with different sized disks, but it will treat all the disk sizes based on the smallest sized disk. If you included all 4 of your disks - the 8TB disks would function as 4TB disks. Once you were able to replace those 4's with 8's, your pool size would expand automatically.

 

[echelon5]

pity you didn't buy 4 4TB drives instead if two 8s

Then you could use 6x4TB Z2 and have 16TB usable.

True, but this also doubles as a test environment for a small business and over there I need the space.

 

[Stux]

what you can do is partition the 8s into 2x 2x 4TB

Then for example make a raidz with a 4TB from each drive and a separate mirror with the remaining 4TB on each 8.

Other solutions are possible

 

[Ericloewe]

what you can do is partition the 8s into 2x 2x 4TB

Then for example make a raidz with a 4TB from each drive and a separate mirror with the remaining 4TB on each 8.

Other solutions are possible

That's still a very bad idea. At the very least, performance would be atrocious.

 

[nojohnny101]

Wouldn't I survive if both 4 TB failed? That's how I understood RAIDZ1: I'd have 3 vdevs out of which 1 vdev is the 2 x 4 TB striped. If 1 x 4 TB fails, the entire vdev fails, so I have to rebuild it by replacing the faulty drive. If 1 x 8 TB fails while I'm rebuilding the stripe vdev, the whole pool is gone.

Sorry I should't have made the statement in regard to this because I made it while assuming everything was part of one pool.

As previously mentioned, raidz1 is scary with 8tb drives. I would say leave it as mirrors (as @gpsguy mentioned), this seems optimal given your circumstances and constrained budget.

 

[Scharbag]

Sorry I should't have made the statement in regard to this because I made it while assuming everything was part of one pool.

As previously mentioned, raidz1 is scary with 8tb drives. I would say leave it as mirrors (as @gpsguy mentioned), this seems optimal given your circumstances and constrained budget.

A mirror with 8TB drives is still scary when you only have 2 disks. Just a little less scary than a 3 disk Z1.

You could do a stripe of mirrors to create 1 pool and then when funds allow for it, swap out the 2 4TB disks with 2 new 8TB disks (on at a time) and then have ~16TB gross space (remember the 80% full rule too).

And, unless you need the IO performance, I personally prefer a Z2 pool setup to mirrors.

Cheers,

 

[nojohnny101]

A mirror with 8TB drives is still scary when you only have 2 disks. Just a little less scary than a 3 disk Z1.

Right, nothing about this situation breed confidence.

And, unless you need the IO performance, I personally prefer a Z2 pool setup to mirrors.

+1 for this.