SOLVED Raid Z Advice

[Chrismal]

Hi
Have been testing out FreeNAS on a test machine for a while and all is great. Now I read around but cant really find good info so I ask you guys that have experience, Is it dangerous to use 4tb drives in raid z1 ? and if I use that what do you guys think the resilvering time would be with 4 of them?

Thanks a lot

 

[Jailer]

It all boils down to basic risk assessment. How important is your data? Are you comfortable putting your data at risk only having one drive worth of redundancy? Others can give all kinds of opinions but ultimately you are the one that's going to have to determine if it's worth the risk.

 

[Chrismal]

Thanks for your reply, My important data are all backed up to a offsite backup, but yes it is still a big hassle to put all the data back. So in your opinion raidz 1 is it a high risk? using 4tb drives can get expensive to loose 2 for parity

 

[Jailer]

So in your opinion raidz 1 is it a high risk?

In my opinion yes with large capacity hard drives.

Maybe we should ban large capacity hard drives to solve that problem.......

 

[Chrismal]

"Maybe we should ban large capacity hard drives to solve that problem......."

Yes loooll that would solve it. Sorry for my last question but what config would you recommend for large drives ?

 

[Jailer]

RAIDZ2 at a minimum. But again, that's my comfort level, yours may be different.

 

[nightshade00013]

Maybe we should ban large capacity hard drives to solve that problem.......

ROFLMMFSOBAO

But I agree RaidZ2 is my minimum for 4TB drives and to me a 8TB or 10TB drive puts you in the RaidZ3 minimum range. You may also want to think about expansion. If you have an idea that you will want to add a second vDev it may be worthwhile to go up to a RaidZ3 now so that you just need to add more drives to create a second vDev and expand.

I imagine that at our current rate we will need a RaidZ4 maybe even RaidZ5 by 2025 unless the chance for URE's goes down as I figure we will be seeing 20TB+ drives by then.

 

[Jailer]

ROFLMMFSOBAO

I knew at least you would get that. ;)

 

[Bidule0hm]

ROFLMMFSOBAO

But I agree RaidZ2 is my minimum for 4TB drives and to me a 8TB or 10TB drive puts you in the RaidZ3 minimum range. You may also want to think about expansion. If you have an idea that you will want to add a second vDev it may be worthwhile to go up to a RaidZ3 now so that you just need to add more drives to create a second vDev and expand.

I imagine that at our current rate we will need a RaidZ4 maybe even RaidZ5 by 2025 unless the chance for URE's goes down as I figure we will be seeing 20TB+ drives by then.

Fortunately, regarding UREs during rebuild, it doesn't work like that, it's not linear. The RAID-Z2 offers sufficient protection, even with 10 TB drives. That's because the problem of RAID-Z1 is that when one a drive is failed you don't have any redundancy anymore so an URE can be really bad. With RAID-Z2 it would take two UREs on two drives (one on each drive) at the exact same time and at the exact same spot on the data to be a problem. That's very very very unlikely, there's others problems far more likely than that you need to worry before this one.

 

[Chrismal]

Thank you guys for all your input, Looks like raid Z 2 will be my choice, any ideas on how long rebuild/ resilver time would be on example 8 4tb drives ?

 

[Johnnie Black]

any ideas on how long rebuild/ resilver time would be on example 8 4tb drives ?

Depends mostly on how much data they have, this was one of my last ones, pool is 8 4TB WD Blues in RAIDZ2:

Code:

scan: resilvered 2.00T in 10h20m with 0 errors on Wed Nov 29 00:39:26 2017

 

[Chrismal]

@Johnnie Black

Thanks for your great info, just a side question did you run into any problems using desktop drives? that was something I am debating also lol do not really know if the extra cost is really worth it for the NAS drives

 

[Johnnie Black]

Thanks for your great info, just a side question did you run into any problems using desktop drives?

Nope, though I not using FreeNAS for that long, about a year or so, I started with 8 3TB WD Greens and upgraded them all to 4 TB Blues a few months ago, no disk failures so far.

 

[Chrismal]

Thanks all again. Its guys like you that help newbies like me love the product even more :)) keep it up

 

[Bidule0hm]

I've a RAID-Z3 (so RAID-Z2 should be faster) of 8x 3 TB drives and the two resilvers I had to do (one in november 2015 and one two weeks ago) took 6 hours (not so idle pool) and 3.5 hours (idle pool) with a pool filled between 1/4 and 1/3 of the total space.