DragonFly users List (threaded) for 2009-01
DragonFly BSD
DragonFly users List (threaded) for 2009-01
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Re: RAID 1 or Hammer


From: "Simon 'corecode' Schubert" <corecode@xxxxxxxxxxxx>
Date: Mon, 12 Jan 2009 23:20:05 +0100

Konstantinos Pachnis wrote:
I'm curious if RAID 1 (mirroring) really helps to protect data loss. Of course if a whole disk "dies", RAID 1 has the advantage that
I have an identical copy. But what happens if only a sector of one disk
contains bad data. How can the RAID controller decide which is the
correct sector? Or would the disk detect such a case and return an error?



When the controller will try to perform an I/O operation it will fail on the faulty disk (the disk with the bad sector). As a result the controller will be able to decide which is the correct sector.

You're assuming fail-stop errors. If it is a sneaking bit error or something else, it won't notice.


cheers
  simon

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