Messages in this thread | | | From | "Andrei Tanas" <> | Subject | RE: MD/RAID: what's wrong with sector 1953519935? | Date | Tue, 25 Aug 2009 22:22:17 -0400 |
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> >> One thing that can happen is when we have a hot spot (like the super > >> block) on high capacity drives is that the frequent write degrade > the > >> data in adjacent tracks. Some drives have firmware that watches for > >> this and rewrites adjacent tracks, but it is also a good idea to > avoid > >> too frequent updates. > > > > Yet another detail to worry about.... :-( > > it never ends :-) > > > > >> > >> Didn't you have a tunable to decrease this update frequency? > > > > /sys/block/mdX/md/safe_mode_delay > > is a time in seconds (Default 0.200) between when the last write to > > the array completes and when the superblock is marked as clean. > > Depending on the actual rate of writes to the array, the superblock > > can be updated as much as twice in this time (once to mark dirty, > > once to mark clean). > > > > Increasing the number can decrease the update frequency of the > superblock, > > but the exact effect on update frequency is very load-dependant. > > > > Obviously a write-intent-bitmap, which is rarely more that a few > > sectors, can also see lots of updates, and it is harder to tune > > that (you have to set things up when you create the bitmap). > > > > NeilBrown > > > > We did see issues in practice with adjacent sectors with some drives, > so this > one is worth tuning down. > > I would suggest that Andrei might try to write and clear the IO error > at that > offset. You can use Mark Lord's hdparm to clear a specific sector or > just do the > math (carefully!) and dd over it. It the write succeeds (without > bumping your > remapped sectors count) this is a likely match to this problem,
I've tried dd multiple times, it always succeeds, and the relocated sector count is currently 1 on this drive, even though this particular fault happened at least 3 times so far.
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