🚀 go-pugleaf

In article <4j9elv$pc0@corn.cso.niu.edu>,
dgersic@niu.edu (David Gersic) wrote:
>
>[...] During one of the
>BrainShare sessions I was at last year, the presenter explicitly
>recommended removing the mirror, then running vrepair, and re-mirroring the
>disks once everything was ok.
>
>
>When running VREPAIR, recommend breaking the mirror on mirrored/duplexed
>  volumes. Fix one set, then re-mirror. Can use the broken mirror to try
>  other recovery options if needed. Also halves the disk i/o required, so
>  should run faster. Remirror after repair.
>
This is nothing short of insanity, and it is unfortunate that it was posted.
One of the fundamental purposes of mirroring is TO HAVE ENOUGH INFORMATION
TO RECREATE ONE LOGICAL DRIVE FROM TWO PHYSICAL DRIVES.  Never, ever break
the mirror except as a last resort.  Lets say that Fat sector one is busted
on drive 0's first volume, and fat sector two is busted on drive 1's first
volume, and that 0 and 1 are mirrored together.  If the mirror were broken and
the drives vrepair'ed separately, then it is possible that both volumes 
would get the dreaded "hole in fat" error.  However, if they were 
vrepaired together, then you would have a complete drive when done.

There is no logic to breaking the mirror for a vrepair.  There is no point
in having mirrored drives if you break the mirror for vrepair.  Only break
the mirror in the event of a partial or complete hardware failure on the drive.

Remember that once a mirror is broken, it CAN NOT be put back together, you
CAN NOT go back.  You can only recreate the mirror fresh, which WILL WIPE
OUT ALL INFORMATION ON THE SECOND DRIVE.

I am not saying that David is confused or misinterpreting what he heard,
I am merely saying that the information he posted is the exact opposite 
of correct.