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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RE: What about 5-way RAID?
by jwwf on Mon 18th Jan 2010 21:43 UTC in reply to "What about 5-way RAID?"
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I have an idea, how about adding just a little more RAID?

I got a great idea.

Lets write an extra copy of every write somewhere....and the cool things with this design is that reads will be TWICE as fast since the data exists in two different places, also its even more secure than RAID7 because you can loose not just 2or3 disks but up to ONE HALF of all your disks and still have your data.

I should patent this idea.

/seriously at some point it just makes more sense to standardize on RAID 10 doesn't it?

The simplicity of the algorithms of the failure modes for coding in the storage devices alone is less complex/more reliable.

I'm starting to think that 3 way mirroring is not crazy, like the article says:

For the same reasons that make triple-parity RAID necessary where RAID-6 had sufficed, three-way mirroring will displace two-way mirroring for applications that require both high performance and strong data reliability.

In the ZFS context I can see the value of 3 way mirroring just because a 2 way mirror wouldn't be able to recover a checksum error during a reconstruction, just as with single parity raid. On the other hand, in most cases I think I would feel just fine with 2 way mirror and a good backup.

Also, looks like it's not just Sun on the triple parity path:

Only skimmed the patent, but it seems like this netapp implementation uses only XOR, like RAID-DP I think, which is interesting.

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