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Barriers and journaling filesystemsBarriers and journaling filesystemsPosted May 21, 2008 20:04 UTC (Wed) by nix (subscriber, #2304)Parent article: Barriers and journaling filesystems
Of course, md also doesn't support barriers for raid5/raid6, which means that using RAID actually *reduces* reliability in some respects. This is somewhat irritating, but also hard to fix: barriering all the constituent devices when a barrier comes in from the higher level isn't good enough on raid5, because if one drive loses power before the other you still have data corruption. (In practice this too is rare enough that it takes explicit torture tests to trip it unless you're very unlucky.)
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Barriers and journaling filesystems Posted May 24, 2008 9:10 UTC (Sat) by Xman (guest, #10620) [Link] I don't see the problem with the power failure scenario. If you encounter a barrier at an MD device, I'd think you would essentially not submit IO to the underlying devices until such time as all I/O's prior to the barrier had completed. In that scenario, at the first sign of a power failure effecting *any* of the drives, I'd start reporting I/O errors and be free of any guarantees whatsoever.
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