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."
Thread beginning with comment 404874
To view parent comment, click here.
To read all comments associated with this story, please click here.
RE[2]: RAID Z
by Laurence on Tue 19th Jan 2010 10:20 UTC 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

RE[3]: RAID Z
by gilboa on Tue 19th Jan 2010 14:37 in reply to "RE[2]: RAID Z"
gilboa Member since:
2005-07-06

I'm not quick to dismiss ZFS.
I actually have a OpenSolaris VM w/ZFS on this machine (under Linux/KVM).

I am saying that ZFS is not the solution to everything.
It cannot replace hardware RAID controllers.
Some people (like me) have major misgivings about the lack of separation between the disk level (E.g. Hardware / Software RAID) and FS layer. (E.g. NTFS, ext4, etc).
And last and not least, *Solaris is also an OS. And you don't select an OS just because it has a shiny file system.

- Gilboa

Edited 2010-01-19 14:46 UTC

Reply Parent Score: 2

RE[4]: RAID Z
by computeruser on Tue 19th Jan 2010 15:18 in reply to "RE[3]: RAID Z"
computeruser Member since:
2009-07-21

It cannot replace hardware RAID controllers.

For some applications, ZFS can be a better (cheaper) fit than hardware RAID.

Some people (like me) have major misgivings about the lack of separation between the disk level (E.g. Hardware / Software RAID) and FS layer. (E.g. NTFS, ext4, etc).

If you don't like it, then why don't you explain why you think it is a bad idea instead of trolling?

And last and not least, *Solaris is also an OS. And you don't select an OS just because it has a shiny file system.

No one said "Everyone should use Solaris because it has ZFS". The first post mentioning ZFS simply mentioned that ZFS now has triple parity in OpenSolaris.

Reply Parent Score: 1

RE[4]: RAID Z
by Laurence on Tue 19th Jan 2010 15:41 in reply to "RE[3]: RAID Z"
Laurence Member since:
2007-03-26

I'm not quick to dismiss ZFS.
I actually have a OpenSolaris VM w/ZFS on this machine (under Linux/KVM).

I am saying that ZFS is not the solution to everything.
It cannot replace hardware RAID controllers.


While I do see where you're coming from, I think you've over-racted to the opening post as nobody was suggesting that ZFS was the solution to everything.
We were just saying that currently there is a solution to the lack of triple parity RAID and that solution is ZFS. It was a very specific point he was making rather than the generalised "ZFS will solve world debt" type evangelical speak that you're (understandably) sick of reading.

Sure there's needs for other solutions and standards - nobody disagrees with that. But the fact remains that ZFS DOES address the triple parity problem.
So personal opinions of ZFS aside - the original poster was spot on with his comments


And last and not least, *Solaris is also an OS. And you don't select an OS just because it has a shiny file system.


Actually you do if the purpose of an OS is to serve files.

Choosing an OS is about selecting that system has the right tools to do it's specific job the best.
So if you need a server with a file system such as ZFS, then selecting *Solaris because of it's FS is the correct decision to make. Just as if you want a media centre, you'd be more interested in graphics and sound card support than it's file system.

Besides, you talk as if you can't get samba, apache, et al for *Solaris, which clearly isn't the case.

Reply Parent Score: 2

RE[4]: RAID Z
by Kebabbert on Tue 19th Jan 2010 17:33 in reply to "RE[3]: RAID Z"
Kebabbert Member since:
2007-07-27

Why can you not replace hardware raid controllers? Dont you know that ZFS protects against much errors than hardware raid? I would not trust hardware raid, actually.

Here is another presentation on Silent Corruption from the CERN guy (their large physics multi billion machines produces huge amounts of data, imagine corrupted data worth of billion of dollars). He concludes that checksums (hardware raid) is not enough. You need end-to-end checksum (ZFS). He talks about they get corrupted data on their Linux rack servers, silently:

https://indico.desy.de/getFile.py/access?contribId=65&sessionId=42&r...


Even better; here is a website explaining how bad raid-5 is, and lots of shortcomings hardware raid has:
www.baarf.com
Lots of sysadmins explains technical details there.

Edited 2010-01-19 17:36 UTC

Reply Parent Score: 2