On Sun, 10 Nov 2013 16:36:35 -0600 Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx> wrote: > On 11/10/2013 2:34 PM, NeilBrown wrote: > > On Sun, 10 Nov 2013 13:17:21 -0600 Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx> > > wrote: > > > >> Also, I see little/no value in running a scheduled mdadm check on a > >> RAID1 array. Any problems with RAID1 will be due to one of the disks > >> beginning to fail in some mode, usually requiring sector relocation. > > > > I think scrubbing has value on any RAID with redundancy. > > That's a bit... redundant, Neil. :) RAID0. Sadly a name that is used, even though it is an oxymoron. > > > The firmware can only relocate a sector if it reads it when it is marginal > > but not yet completely lost. If a sector is not read for a long time and > > during that time the media degraded beyond recovery the firmware cannot do > > anything. But RAID1 can - it can get it from the other device. > > But is a scrub required for this? Isn't this exactly what occurs during > normal operation with md/RAID1? I.e. a read fails with disk error, so > we grab the sector from the mirror? So what advantage is there to > scrubbing md/RAID1? > If scrubbing finds and repairs a (rarely accessed) bad sector on one drive before the other drive dies completely, that is a win. NeilBrown
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