Raid 5 performance

[The Edge of the Ice]

On Tue, 21 Sep 2004 15:01:17 -0400, Martin Duclos <tchitow-PkbjNfxxIARBDgjK7y7TUQ at public.gmane.org> wrote:
> I've decided to install a raid 5 on a file server at home. CPU is pentium
> 120MHz with 64M ram. I know it's rather scarce but my question is, is there
> a way to measure where the biggest performance hit will be? I want to know
> of a way I can monitor which compenent is the bottleneck. Will increasing
> memory improve performance? Will faster CPU make a difference? I'm looking
> for a real technique (ie numbers) from which I can get a better
> understanding. I've looked at google groups and all I can really find are
> opinions and vague references to "if you have this or that it might give you
> better..."

How about replacing the whole motherboard/cpu/ram set?  You'll probably have
much better luck doing that than finding reliable upgrade components, and the
whole system will run a LOT faster for it.

For $230 (including tax) you could get yourself a Celeron 1.7GHz with 256MB of
RAM, and some generic VIA chipset (with onboard video) that will severely
outperform that old board.  If you don't cheap out on the mobo quite so much
(I don't think I'd buy a $60 mobo, personally), you can get something that will
probably be more reliable, too.  I really wouldn't consider RAID5 on something
like that.  RAID5 only becomes interesting with 3 or more drives, too.  Look for
a 3ware or highpoint card, as mentioned in one of the other threads.  That will
solve a LOT of headaches, and help to keep your data safer.  Before even
going to RAID5, go and purchase a UPS.  They can be had for $120, and will
probably provide much better protection for your dollar than RAID5.

If you really do want your data to be secure, you might consider just getting a
pair of drives and mirroring between the two.  Just be careful how big you go,
though, since the old ATA interface can't handle anything over 132GB IIRC
(not to mention the issues you might have booting a kernel beyond 8GB).

That being said, increase the RAM.  Fileserving would do best to have as
much caching as possible, since it's IO intensive rather than CPU intensive.
Just don't expect scp transfers to go fast (crypto will be your bottleneck);
use nfs or samba.

-- 
taa
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