PERC 4e/DC in 2850 - lost 1 disk, RAID5 array failed

[Bill Carlson]

On Fri, 7 Jul 2006, Johan De Meersman wrote:

> I'm wondering about something else, though: in the event of a multi-disk
> failure on a raid 5, shouldn't it be possible to still retrieve the part
> of the data whose integrity hasn't been lost ? I've been lucky enough
> not to encounter the situation yet, but I can imagine it could come in
> handy, for example on image-serving webservers.

No, in the event of a multi-disk failure, data retrieval is gone. Recall
that RAID 5 means chunking the data in N-1 parts, where N=number of drives
and writing a chunk to N-1 disks plus a parity chunk to the Nth disk that
would allow any one chunk to be reconstructed given the other N-1 chunks.
If two disks are gone, 2 chunks or a chunk and the parity are missing, no
way to reconstruct anything. I think it would be challenging to even get a
piece of a file, let alone a whole file.

Bill Carlson
-- 
Systems Administrator bill-carlson at uiowa.edu  | Anything is possible,
HCIS                                          | given time and money.
University of Iowa Hospitals and Clinics      |       
Opinions are mine, not my employer's.         |