[mythtv-users] Why RAID 5 stops working in 2009

[Thomas Fjellstrom]

On Thursday 23 October 2008, John Drescher wrote:
> >> Erm, if it's raid 6, wouldn't you need 3 drives to fail for it to kill
> >> you?
> >
> > The way I understand RAID-6, the failure would have to be:
> >
> > 1 dead drive
> > 1 URE on another drive
> > 1 URE on yet another drive in the same stripe as the above URE
>
> Highly unlikely and preventable. I mean you can have both hardware and
> software check the drives every once and awhile so you if it finds
> drives with UREs (bad sectors that can not be read - drive should have
> fixed them on the first read that it detected a problem)  it will kick
> the bad drive from the array then.
>
> Also even in this unlikely case with mdadm you should be able to copy
> the bad drives to new drives and force the arrays to sync even with
> the missing data. I am not sure if hardware controllers allow you to
> sync disks that have problems like this.

If that sector is a parity sector, and its lost its original data, a restore 
is going to destroy a lot of data from what I've heard.

>
> John
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-- 
Thomas Fjellstrom
tfjellstrom at shaw.ca