[SATLUG] raid questions

Brad Knowles brad at shub-internet.org
Sat Jan 12 17:07:50 CST 2008


On 1/12/08, Chris Lemire wrote:

>  I'm being told that my raid setup is a bad idea. Is this true?
>
>  http://forums.fedoraforum.org/showthread.php?p=941593#post941592

Certainly, you're not going to see any kind of real performance 
speedup with RAID-0 on one slice of two disks, where you're doing 
RAID-1 on all the other slices.

I don't think that you'd physically hurt the disks in question, but 
with all the other slices writing each piece of data to both disks 
simultaneously, and one slice that is trying to simultaneously write 
different sets of data to the two disks, there's going to be a big 
performance hit.


I think that "lazlow" is probably right that you should either run 
all RAID-0 or all RAID-1 on a given pair of disks, and not try to mix 
the two types of RAID on different slices.

But I see this as more of a performance and wasted resources issue, 
and not so much an issue of causing physical damage to the disks.


That said, maybe the Linux RAID software really is flaky enough that 
doing both RAID-0 and RAID-1 on different slices of the same pair of 
disks would potentially risk causing real damage to the filesystem 
data being written (although not to the disks themselves), but I kind 
of doubt that -- the Linux RAID software has been around a fairly 
long time, and if this were a real issue then I think it would have 
been addressed a while back.

-- 
Brad Knowles <brad at shub-internet.org>
LinkedIn Profile: <http://tinyurl.com/y8kpxu>


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