RE: Parity Set Configuration Advice

["DeLong, Eric" <EDeLong@xxxxxxxxxxxxxxx>]

Rob, I believe there's still potentially a performance advantage with
mirroring, since you've essentially doubled the arms available for read IO.
I don't know if this still applies with the new controllers, but it's
probably negligible in today's systems.  I know that in the past, the ideal
scenario for mirrored DASD was to have each half of a mirrored pair running
on different controllers, in separate cabinets.  As I recall, the idea was
to protect disk access in the event of power supply problem in one of the
two cabinets.... Something like that.... 



Eric DeLong
Sally Beauty Company
MIS-Project Manager (BSG)
940-898-7863 or ext. 1863



-----Original Message-----
From: rob@xxxxxxxxx [mailto:rob@xxxxxxxxx]
Sent: Tuesday, April 20, 2004 1:34 PM
To: Midrange Systems Technical Discussion
Subject: Re: Parity Set Configuration Advice


With as many drives as we've replaced, hot, with RAID; I don't see any 
problems with data integrity.

Does anyone, with newer hardware, see a point to mirroring instead of RAID 
anymore?

Rob Berendt
-- 
Group Dekko Services, LLC
Dept 01.073
PO Box 2000
Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





"James H H Lampert" <jamesl@xxxxxxxxxxx> 
Sent by: midrange-l-bounces+rob=dekko.com@xxxxxxxxxxxx
04/20/2004 12:57 PM
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Re: Parity Set Configuration Advice






> Isn't there downtime associated with mirroring?  Meaning can you:
> -remove the old drive
> - add the new drive
> - and get the mirroring restarted
> without any downtime?  Because with RAID, we can, and have.

As I recall, when we lost a mirrored "hat" drive on our 510, we were able
to hot-swap in a replacement. But I may have been mistaken. We're more
concerned with data integrity than with whether or not we have to re-IPL,
and can take some downtime.
Now if only the controller permitted parity groups OF mirrored pairs . . . 
.

--
JHHL


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