On Mon Jan 31, 2011 at 03:21:51PM +0000, Robin Hill wrote:
> On Mon Jan 31, 2011 at 01:00:13PM -0200, Roberto Spadim wrote:
>
> > i think make two very big raid 0
> > and after raid1
> > is better
> >
> Not really - you increase the failure risk doing this. With this setup,
> a single drive failure from each RAID0 array will lose you the entire
> array. With the reverse (RAID0 over RAID1) then you require both drives
> in the RAID1 to fail in order to lose the array. Of course, with a 4
> drive array then the risk is the same (33% with 2 drive failures) but
> with a 6 drive array it changes to 60% for RAID1 over RAID0 versus 20%
> for RAID0 over RAID1.
>
And I managed to get my maths wrong. Even for a 4-drive array, RAID1
over RAID0 will have a 66% 2-drive failure chance, versus 33% for RAID0
over RAID1.
Cheers,
Robin
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( ' } | Robin Hill <robin@xxxxxxxxxxxxxxx> |
/ / ) | Little Jim says .... |
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