Re: Data transfer across disks.

["Neil Palmer" <neilp@xxxxxxxxxxx>]

Neil,

I would have gone for one more 6824, to give you 8 disks in the RAID set, and then you could spread the parity information over 8 drives instead of 4 for better performance.  (would have to stop & restart Device Parity protection on that set after adding the new disks to spread parity striping over the 8 disks).
It sounds like you should have sufficient disk arms in the system.

Neil Palmer      DPS Data Processing Services Canada Ltd.
50 Acadia Avenue, Ste.102                   AS/400~~~~~
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http://www.DPSlink.com     iSeries 400  The Ultimate Business Server

"Carley, Neil" <carleyn1@Midas-Kapiti.com> Sent by: owner-midrange-l@midrange.com 2000/12/01 05:19 Please respond to MIDRANGE-L

To:        "'MIDRANGE-L@midrange.com'" <MIDRANGE-L@midrange.com>         cc:                 Subject:        Re: Data transfer across disks.

Hi Neil, 
thanks for the reply and in answer to your questions:

>Question - you're adding only three 6824's, so no requirement for RAID-5 on
these new disks ?? 
>That seems strange as the 9337's are RAIDed.  Unless you already have some
6824's in a RAID set >and are adding 3 disks to that set ? 
>If so, how many disks will there be in that 6824 RAID set ? 
>Also, even though the new disks are faster than the 9337's, have you
considered the impact on >performance of replacing 24 disk arms with 3
(especially three of the 17.5GB drives) ?  

Yes their will be a requirement for the new disks to be RAIDed, we curently
have 4 x #6714's already on the system so the new disks will be added into
that raid set (assured by IBM that these disks are the same - just different
part no's) giving us 7 disks in the new RAID set.
As for the performance issue you mention we also have 18 #6607 disks on the
primary ASP so after the work is complete we will still have 25 disk arms on
the ASP, hopefully we will not see any performance degradation due to disk
arms. At the moment we have no problems in this area with our disk arms
running on average at about 10% 
This process is a short term stepping stone for us really to get some
additional DASD and remove the older unreliable 9337's from our main ASP, we
are in the process of planning a bigger upgrade whick will involve an
expansion tower to add further DASD as our 720 box will be full after next
w/e.

thanks again 

Neil