Re: Running check and e2fsck simultaneously

[NeilBrown <neilb@suse.de>]

[-- Attachment #1: Type: text/plain, Size: 1342 bytes --]

On Sun, 10 Nov 2013 16:36:35 -0600 Stan Hoeppner <stan@hardwarefreak.com>
wrote:

> On 11/10/2013 2:34 PM, NeilBrown wrote:
> > On Sun, 10 Nov 2013 13:17:21 -0600 Stan Hoeppner <stan@hardwarefreak.com>
> > 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

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 828 bytes --]