Re: RAID 1 or Hammer

["Simon 'corecode' Schubert" <corecode@xxxxxxxxxxxx>]

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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