How would you set up a large storage?

[hai]

Hi all,

after reading all that:

http://www.zdnet.com/blog/storage/why-raid-5-stops-working-in-2009/162
http://www.zdnet.com/has-raid5-stopped-working-7000019939/
http://community.spiceworks.com/topic/187502-type-of-raid-is-best

it is clear that RAID5 is dead and RAID6 not much better. Hence raidz and raidz-2 as well. OK, depending what you want/need. 3 x 300GB for raidz might be all right but I have something bigger in mind.

So, let's say you have 24 slots filled with 24 4TB disks. Connected via fibre channel to a capable (tons of RAM) server and backups of course.

What would you do? One or more Striped Mirrored Vdev Zpools? A couple of raidz-2 with spares?

Thanks for your opinions!

hai

 

[cyberjock]

spares are pointless since they don't come online automatically.

I'd do 6 or 10 disk RAIDZ2s.

 

[hai]

Well, you get an email from the system first and then you have time to add the spare.

Why not a striped mirror?

 

[cyberjock]

Sorry, when people say "spares" they are talking about "spares" in ZFS. Those don't work right now.

If you are saying spares with stuff on the shelf, that's fine(that's what I do).

 

[hai]

IC. Then it does even make less sense to use a riadz-2. Such a storage is often not next door so that you can quickly swap a HD.
Will that work in an upcoming release of FreeNAS?

 

[Yatti420]

I'll take a z2pool over z1 any day..

Sent from my SGH-I257M using Tapatalk 2

 

[Ericloewe]

RAIDZ2 is fine, but feel free to move to RAIDZ3 if you're paranoid.

Just keep vdevs at less than 11 drives (for performance, RAIDZ2s of 4, 6 or 10 drives, RAIDZ3s of 5, 7 or 11 drives) and you'll be fine. Join the vdevs in as few pools as you feel would make sense, balancing convenience with safety (one vdev fails, the whole pool is lost).

If performance is the requirement, stripes and mirrors in whatever configuration balances your speed and data safety needs.

 

[hai]

Yep, raidz-1 is completely out of question.

Right I forgot about raidz-3. Well, according to what I read about URE raidz-2 doesn't really help. Let's say I would have a raidz-2 with all 24 disks (stupid, I know) then two can fail which is a bad ratio. But I'd have 22 x 4TB = 88 TB. If I'd set up 6 x raidz-2 then reliability would be half decent but just 48 TB. A striped mirror would be 48 TB as well and 6 x raidz-3 80 TB.

I found a calculator btw. raidz-3 is the winner if it comes to reliability though.

hai

 

[Ericloewe]

Yep, raidz-1 is completely out of question.

Right I forgot about raidz-3. Well, according to what I read about URE raidz-2 doesn't really help. Let's say I would have a raidz-2 with all 24 disks (stupid, I know) then two can fail which is a bad ratio. But I'd have 22 x 4TB = 88 TB. If I'd set up 6 x raidz-2 then reliability would be half decent but just 48 TB. A striped mirror would be 48 TB as well and 6 x raidz-3 80 TB.

I found a calculator btw. raidz-3 is the winner if it comes to reliability though.

hai

You do not want 12+ disk vdevs. In any case, you need at least 2 vdevs. RAIDZ2 is perfectly fine for current drive sizes and vdev sizes. Of course, it's not meant for huge vdevs, but you shouldn't be using huge vdevs in the first place.

 

[cyberjock]

Well, according to what I read about URE raidz-2 doesn't really help

You realize that the whole "RAID5 is dead and RAID6 is the fix is because it fixes the URE problem? So how do you make a statement that so blatantly goes against everything everyone says about URE.... not to mention the reality we've seen in the forums. ;)

 

[hai]

I know that huge vdevs make no sense. That was more like theoretical thoughts.

Well, according to the first article above RAID6 does not help:

"So now what? The obvious answer, and the one that storage marketers have begun trumpeting, is RAID 6, which protects your data against 2 failures. Which is all well and good, until you consider this: as drives increase in size, any drive failure will always be accompanied by a read error. So RAID 6 will give you no more protection than RAID 5 does now, but you'll pay more anyway for extra disk capacity and slower write performance."

Mhm.

hai

 

[Ericloewe]

RAID6 solves the problem for a few more years.

If hard drives keep growing without reducing error rates, in a few years RAID6 will be where RAID 5 is today. Today, RAIDZ2 is good enough for most applications.

 

[hai]

All right then. Conclusion:
If you're paranoid then raidz-3 otherwise raidz-2 with up to 10 drives. When 6TB drives are cheap and 8TB quite common then we talk again;)