[ILUG] Dell PERCs and Linux
paul at clubi.ie
Sun Jun 18 02:29:57 IST 2000
On Sun, 18 Jun 2000, David Murphy wrote:
> I have only ever argued that 2-disk RAID1 is a better choice than
> 3-disk RAID5.
and on which criteria were you arguing? speed wasn't it?
"RAID5 is relatively safe and cheap. It's not relatively fast."
> Nobody has yet posted 2-disk RAID1 v 3-disk RAID5 numbers on the same
one Vs. the other, no. But we have at least seen the RAID5 benchmarks
4 disk RAID5: 37MB/s block read, 8MB/s block write.
3 disk RAID5: 34MB/s block read, 17MB/s block write.
That clearly shows that RAID5 can be /very/ fast, contrary to what
> therefore there has been nothing but speculation on all
> sides, mine included.
no. I have /seen/ the figures from linux software raid with my own
2 disk RAID1 wasn't much of an improvement over single disk,
3 disk RAID5 was a vast improvement. (~ x 1.5).
> I have benchmarked nothing, and haven't
> suggested otherwise. I said that I did not know what linux did with
> reads from a RAID1 device. I don't know how you get from there to a
> suggestion that Linux software raid is deficient.
s/is defficient/perhaps suboptimal/
that was the implication anyway.
Paul Jakma paul at clubi.ie
PGP5 key: http://www.clubi.ie/jakma/publickey.txt
I can't decide whether to commit suicide or go bowling.
-- Florence Henderson
 all arrays had write-through set. Write performance would be
better if they were write-back.
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