Help with choose correct storage configuration

[john_malkovich]

Hello guys,

I have 4 x 6Tb with 7200rpm (3 x HGST HUS726060ALE614 + 1 x HGST HUS726T6TALE6L4) and 4 x 4Tb with 5400rpm (WDC WD40EFRX-68WT0N0) disks for new NAS installation.

My requirements: raid6 protection level, maximum space, low perfomance degradation and combined in one pool for comfortable management (if possible)

I think about few options:

1. 4 x 6Tb RAIDZ2 pool and 4 x 4Tb RAIDZ2 combined in one pool
2. 8 x 4Tb RAIDZ2 pool and 4 x 2Tb RAID10 in two pool
3. 4 x 6Tb RAIDZ1 pool and 4 x 4Tb RAIDZ1 combined in one pool
4. ???

Problem:

1. Different rpm's
2. Possible problems with perfomance and protection

Can me advice correct storage configuration with my requirements?

Thanks!

 

[JohnDigital]

Figure it from a different perspective with me. That's 40TB of usable raw theoretical space, of which parity space will consume half in 2 pools, 20TB, that's forever unless you resilver in larger disks always losing half your space. IMHO that's a waste. I feel like 2 disks per 8 is about right. Its really a question of how stable is your hardware, and how lazy are you? Will you be broke for 6 months when a disk starts failing? Will you know when a disk is failing? I turned alot of friends and family onto this and they are always asking goofy questions and running the goofiest configs crashing pools and such. Then want me to fix it. I am now mostly saying start over, you must learn, or pay.

Now what if we combined all disks in one Z2 pool mismatched (certainly not officially recommended and you'll get a warning in the GUI about doing this) of 8 Disks (6x4TB=24TB) with 2 for parity(8TB). The rest (8TB) is technically lost, for now. It results in more space and less parity, but with the option of replacing the 4TB disks down the road as they fail, or if space is needed soon, you could silver in 4 6TB disks to expand the pool by a real ~12TB.

Then repurpose the old 4's, or my personal favorite resell on eBay with the SMART stats in a lot, thus covering some cost of your new 6's. I did this from 2's to 3's to 5's. And now 5's are starting to fail and im replacing with 6's. Your not able to sell bad drives are you? You can if clearly stated for parts. And people buy them, maybe not for much but there's still value there. High mileage disks? Include SMART stats and people will still buy if its clean and stated USED not refurbished or any of this other they try to pull.

I'm sure there are those will say blah blah different RPMs and sizes this and that, it hasn't made a noticeable difference to me and I've let a new pool go this way for awhile now and I notice nothing. Been trying different brands of disks mismatched in, and have had no issues. Its also smart as a 6TB disk which I still consider "expensive" in a couple years as tech progresses and you start to fill up your ~24TB pool-- they'll be had for dirt cheap all over kind of like 2s, 3s and 4s are now. In a couple years it'll be 6s 8s and 12s, about the time your current disks start failing.

Just my .02 pennies. Whatever you decide will ultimately be right for you.

 

[Patrick M. Hausen]

8 x 4Tb RAIDZ2 pool and 4 x 2Tb RAID10 in two pool

There is no RAID10 in ZFS. You could use another RAIDZ2 or two mirror vdevs. Please just forget that "RAID" terminology.

But ...

You cannot assign parts of disks to different pools. If you create an 8x 4T RAIDZ2 pool, the remainder of your 6T disk is lost.
You can replace your 4T disks with 6T ones later and automatically expand the available space, though.

 

[ChrisRJ]

Option 2 does not work, as @Patrick M. Hausen explained above, and option 3 collides with your requirements. I would probably throw all disks in one VDEV (and pool) with RAIDZ2. That gives 24 TB net storage and good protection.

 

[john_malkovich]

Thanks guys for advices, my current decision is one pool with 2 vdev: 4x4Tb (raidz1) and 4x6Tb (raidz1) = 12Tb + 18Tb = 30Tb. Is possible?
I accept risk with two disks failure in one vdev and I will make backups regularly.
I think is best offer for my situation.

 

[Patrick M. Hausen]

I personally wouldn't do RAIDZ1, but your setup will work as you intend, yes.

 

[ChrisRJ]

I would like to second what @Patrick M. Hausen says. You have eight drives and the likelihood of something going wrong is not that small. Also, the configuration you laid out would be in direct conflict with your explicit requirement of RAID-6 level protection, it would only be comparable to RAID-5.

 

[pschatz100]

If you make one pool with the two RaidZ1 vdevs, and you lose one of the vdevs then you lose the entire pool. That would be more risk than I am willing to accept.

I am a believer in RaidZ2. It is an uncomfortable feeling to replace a disk, and hope that your resilver finishes without incident (or else you lose everything.)