RE: Back to the RAID question

>Kill me now.

Hmmmmmm.....  :)

Joe, you're asking performance questions, and you know the answer to all
performance questions is "it depends." Seriously, what's better for a
server is not necessarily what's better for a single user, and beyond
that, what's better for sequential IO (like a log file) is not
necessarily what's better for random IO. And what's better for read is
not necessarily better for write. And what's better for large-block IO
is not necessarily what's better for small block IO, so in short, it
depends.

If I understand all the proposals you've posted you're looking at a
single logical drive (C:). From a performance point of view you should
also consider separating your machine into two, or ideally three, sets
of spindles, one for system & program, one for swap and one for data.
Obviously these spindles could be a combination of RAID 0, 1 and 5.

FWIW, my machine at home is a 10K SATA drive for system & Program (no
raid, if I loose it I reinstall), two RAID 0 drives for SWAP/TEMP
(again, if I loose a drive I'm toast) but I gain the speed from RAID 0
and data resides on a mirrored pair of drives.

Stop asking "it depends" questions, and buy the darn machine. Unless you
run it side-by-side with one of configured another way you'll never know
if you have the best, worse, or just an average configuration anyway, so
just tell yourself that the one you pick is the fastest and move on.

-Walden


------------
Walden H Leverich III
Tech Software
(516) 627-3800 x11
WaldenL@xxxxxxxxxxxxxxx
http://www.TechSoftInc.com

Quiquid latine dictum sit altum viditur.
(Whatever is said in Latin seems profound.)


-----Original Message-----
From: pctech-bounces@xxxxxxxxxxxx [mailto:pctech-bounces@xxxxxxxxxxxx]
On Behalf Of Joe Pluta
Sent: Tuesday, September 13, 2005 10:48 AM
To: 'PC Technical Discussion for iSeries Users'
Subject: RE: [PCTECH] Back to the RAID question

I'm still bashing my head over the RAID question, though.  RAID 5 is a
better price/performance than RAID 1, and according to IBM, RAID 5
actually tends to outperform RAID 1 due to number of spindles.  So, for
instance, where I to use five 36GB drives ($1500) to create a 146GB RAID
5 array, this would theoretically outperform a two mirrored (RAID 1)
146GB drives ($2000).

More hitches: throw in an extra drive and you get RAID 5E (which has
already been superseded by RAID 5EE).  Better performance, but slower
rebuild time and you lose a drive.  So now the question is this: does a
five-drive RAID 5EE array (108 GB) perform better or worse than a
six-drive RAID 10 array?

Does a four-drive RAID 5EE array outperform a four-drive RAID 10 array?
Does a six-drive RAID 5EE array of 36GB drives ($1800) outperform a
four-drive RAID 10 array of 73GB drives ($2000)?

Kill me now.

Joe