RE: 515 Configuration Funny

As far as i understood it, and i might be wrong here (someone with more
expectise should correct me on this).

Mirroring on the i5 is handled by the OS, and not the disk controller -
this is necessary because i5/OS mirroring can span multiple towers, or
controllers.

So while two write are necessary for a RAID5, this is handled by the
controller - the OS only has to issue a single write request.

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Walden H. Leverich
Sent: Monday, April 16, 2007 6:25 PM
To: Midrange Systems Technical Discussion
Subject: RE: 515 Configuration Funny

ONLY in a HIGH READ environment. Mirroring uses a Read Either, but a

Write Both before the transaction is complete. I'll take a 4 drive

Raid5

over a Mirrored Set or even 2 sets any day.

But why? Clearly the majority of IO in our typical System i business
application is READ.

Also, doesn't RAID5 require 2 writes as well, one for the data and one
for the parity. If you don't write the parity you can't recover the
data.

-Walden