RAID's Days May Be Numbered

storagedude sends in an article claiming that RAID is nearing the end of the line because of soaring rebuild times and the growing risk of data loss. "The concept of parity-based RAID (levels 3, 5 and 6) is now pretty old in technological terms, and the technology's limitations will become pretty clear in the not-too-distant future — and are probably obvious to some users already. In my opinion, RAID-6 is a reliability Band Aid for RAID-5, and going from one parity drive to two is simply delaying the inevitable. The bottom line is this: Disk density has increased far more than performance and hard error rates haven't changed much, creating much greater RAID rebuild times and a much higher risk of data loss. In short, it's a scenario that will eventually require a solution, if not a whole new way of storing and protecting data."

Comments

ZFS

[DiSKiLLeR]

This is something the ZFS creators have been talking about for some time, and been actively trying to solve.

ZFS now has triple parity, as well as actively checksumming every disk block.

Re:ZFS

[DiSKiLLeR]

I thought I should add:

ZFS speeds up rebuilding a RAID (called resilvering) over traditional non-intelligent or non-filesystem based RAIDS by only rebuilding the blocks that actually contain live data; there's no need to rebuild EVERYTHING if only half the filesystem is in use.

ZFS also starts the resilvering process by rebuilding the most IMPORTANT parts first; the filesystem metadata and works its way down the tree to the leaf nodes rebuilding data. This way, if more disks fail, you have attempted to rebuild the most data possible. If filesystem metadata is hose, everything is hosed.

ZFS tells you which files are corrupt, if any are, and insufficient replicas exist to due failed disks.

All this on top of double or triple parity. :)