BTRFS RAID6 coming

I’ve been keeping an eye on btrfs for some time, it provides a next generation file system for Linux that is in many ways equivalent to ZFS on Solaris.  It’s still relatively new, so not something you’d trust irreplaceable data to, but long term it will provide some compelling features:

  • Checksumming of all data and metadata.  As drives get larger the law of averages / large numbers says that some pieces of data will become corrupt.  For media files this isn’t critical, you might get a pixel different on one frame of a movie.  For a spreadsheet or a program it could be critical.  Checksumming will tell you if your data is wrong on disk
  • Integrated RAID support.  RAID 0 and 1 are built-in, and it allows different RAID levels on different directories, and different for metadata v’s data.  RAID5/6 has been “coming” for some time, but not available yet
  • Because the RAID is integrated, and because of checksumming, where a discrepancy is identified between two drives btrfs can pick the correct one to repair from – not only does it make your data redundant, it can sensibly fix it when something goes wrong (md RAID basically randomly picks one block so as to get back in synch)

The RAID5/6 patches have gone up into an experimental tree, which means they’re on the way to the kernel proper, I’d guess maybe 3.10.  Which is huge news.  Refer:

http://lwn.net/Articles/536038/

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