Linked by Thom Holwerda on Mon 18th Jan 2010 16:57 UTC, submitted by wanker90210
Hardware, Embedded Systems ACM's latest journal had an interesting article about RAID which suggested it might be time for triple parity raid. "How much longer will current RAID techniques persevere? The RAID levels were codified in the late 1980s; double-parity RAID, known as RAID-6, is the current standard for high-availability, space-efficient storage. The incredible growth of hard-drive capacities, however, could impose serious limitations on the reliability even of RAID-6 systems. Recent trends in hard drives show that triple-parity RAID must soon become pervasive."
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RAID Z
by garyd on Mon 18th Jan 2010 17:13 UTC
garyd
Member since:
2008-10-22

ZFS is already ahead of the curve as it introduced triple parity RAID in last summer's release of OpenSolaris.

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Reply Score: 4

RE: RAID Z
by gilboa on Mon 18th Jan 2010 22:59 in reply to "RAID Z"
gilboa Member since:
2005-07-06

ZFS is already ahead of the curve as it introduced triple parity RAID in last summer's release of OpenSolaris.


* Sigh *
A. ZFS is not a standard (unlike, say RAID6). It's an implementation. Far worse, it's a patent encumbered implementation of a triple parity RAID level.
B. You'll amazed to hear that most of the world doesn't use OpenSolaris.
C. As far as I remember, OpenSolaris' modified grub cannot boot from ZFS RAID. (And nothing beats losing your boot record + kernel on a production machine, right?)

- Gilboa

Reply Parent Score: 1

RE[2]: RAID Z
by computeruser on Mon 18th Jan 2010 23:52 in reply to "RE: RAID Z"
computeruser Member since:
2009-07-21

ZFS is not a standard (unlike, say RAID6). It's an implementation. Far worse, it's a patent encumbered implementation of a triple parity RAID level.

There is no standard detailing RAID-6, just a widely accepted definition.

ZFS happens to implement something with similar redundancy characteristics to RAID-5 and RAID-6 and also implements triple parity.

You'll amazed to hear that most of the world doesn't use OpenSolaris.

So? That doesn't change that OpenSolaris supports triple parity right now. Since OpenSolaris has networking support, including CIFS, iSCSI, and NFS serving, it can still be useful to those who don't currently use OpenSolaris.

As far as I remember, OpenSolaris' modified grub cannot boot from ZFS RAID. (And nothing beats losing your boot record + kernel on a production machine, right?)

ZFS is not the only way to provide redundancy for a boot partition.

Reply Parent Score: 3

RE[2]: RAID Z
by tylerdurden on Tue 19th Jan 2010 03:18 in reply to "RE: RAID Z"
tylerdurden Member since:
2009-03-17

RAID is not a standard either. What does userbase have to do with anything? Same could be said about linux/BSD/windows whatever... "not everyone uses it"

You can use RAID in your solaris root partition, and then manage extra partitions and their redundancy via ZFS, and yes with triple parity even. If you are putting many TB's of data in your root partition, you deserve what you get.

What the heck do patents have to do with triple parity? I think you just had an anti-solaris narrative and decided discussing triple-parity was a good place to dump it...

Edited 2010-01-19 03:24 UTC

Reply Parent Score: 2

RE[2]: RAID Z
by Kebabbert on Tue 19th Jan 2010 09:51 in reply to "RE: RAID Z"
Kebabbert Member since:
2007-07-27

C) You can mirror your ZFS system disk. That makes it less likely that you loose your production system.

Sure, ZFS has a different license than Linux, so what? ZFS is still open and other OSes use it. If Linux has problem with the CDDL license, so what? Does the whole world revolve around Linux? Why? "If Linux does not support it, it sucks"? Why so ego centric? Use FreeBSD instead than Linux, then. You will get better quality than Linux, and you will get ZFS.

Regarding standards, ZFS is not a standard, but it is open. And you can import your zfs raid into other OSes and export them. Even to CPUs with different endian! Can you do that with an ordinary raid?

And, zfs protects against silent corruption. CERN did a study on 3000 hardware Linux racks, it turned out that 152 of the Linux racks corrupted the data, without even noticing it! CERN noticed this, because they wrote a prespecified bit pattern, and after a short while they noticed differences in the expected bit patterns and the actual raid data. Had they ran the test for longer, they would have seen even more corrupted data! As the CERN guy concludes: ordinary checksums (which raid does) is not enough! You need end-to-end checksums to detect these errors so you can correct them - he suggests zfs as a solution to this problem.
http://storagemojo.com/2007/09/19/cerns-data-corruption-research/

Triple parity is needed because, as disks get bigger, the raids take longer time to repair if a disk breaks. With large disks, it can take over a week to repair the raid! During that time, more stress is on the other drives, so they also break. So two disk parity is not enough - for big drives. If you use small disks, then 1 or 2 disk parity is enough. Triple parity is only needed for large disks > 2TB.

Reply Parent Score: 4

RE[2]: RAID Z
by Laurence on Tue 19th Jan 2010 10:20 in reply to "RE: RAID Z"
Laurence Member since:
2007-03-26


A. ZFS is not a standard (unlike, say RAID6). It's an implementation. Far worse, it's a patent encumbered implementation of a triple parity RAID level.

It's not the standard but it's a standard.
And while I agree with you that an agreed open standard for triple parity RAID is needed, there is at least already a file system available for use which supports such.
Plus at least said implementation is open source (even if it is patent encumbered)


B. You'll amazed to hear that most of the world doesn't use OpenSolaris.

What about FreeBSD or Linux (albeit via FUSE)?
Or how about one of the many other Solaris derived projects from pure Solaris to Nexenta (OpenSolaris plus debian user space tools)?

Besides - if you're business is large enough where triple parity RAID (or lack of) is a serious issue, then I'm sure they can either afford to run a dedicated *Solaris file server (even it's only virtualised) or learn how to run their additional tools on *Solaris.


C. As far as I remember, OpenSolaris' modified grub cannot boot from ZFS RAID. (And nothing beats losing your boot record + kernel on a production machine, right?)

You're right, however OpenSolaris can boot for a ZFS mirror.

And why would you want to boot off your large data drives anyway?
It would make more sense to keep your OS separate from your production data.



Don't get me wrong, I'm not suggesting that there isn't a need for an official standard.
However I'm also saying don't be quick to dismiss ZFS just because it proprietary.

Reply Parent Score: 4