On Wed, 11 Sep 2013 09:32:23 -0300 Henrique de Moraes Holschuh <hmh@xxxxxxxxxx> wrote: > On Tue, 10 Sep 2013, Dan Williams wrote: > > On Tue, Sep 10, 2013 at 11:19 AM, Henrique de Moraes Holschuh > > <hmh@xxxxxxxxxx> wrote: > > > (please CC me on replies). > > > I've been in several situations where it would have been helpful to be able > > > to refresh weak sectors by rewriting the whole md raid component device, > > > without the need to increase array failure risk through a fail+remove+add > > > cycle for the component device. > > > > > > How difficult would it be to implement a "refresh" as a Linux md driver > > > sync_action, pigging back on "check" ? > > > > > > Are there any drawbacks to write-refreshing component devices? > > > > > > > Why is "check" insufficient? If it trips over any bad sectors it will > > re-write them. > > The idea is to rewrite the sector _before_ it goes bad. > > Consumer SATA HDDs nowadays not only apparently fail to properly remap > sectors because they don't track anymore that some sectors in that subtrack > were reported uncorrect a number of times (and thus are "weak"). They also > appear to not write-refresh sectors that required ECC correction, except > maybe during an offline SMART test routine. > My view on this is that it has nothing to do with RAID. If it is valuable to "write-refresh" a device in a RAID array, then it would equally make sense to write-refresh a device that wasn't in a RAID array. So any solution to this should try to address the whole problem. NeilBrown
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