RE: Change from mirror to RAID

Hi Doug:
Thank you very much for your detailed and quick reply.  Sounds like I have a
plan.  I think I will take your advise and do it exactly the way you
describe.  I was under the impression that I could only put 4 drives in the
7117 cabinet.  I may just go ahead an add 8 drives (6607) in the 7117 and
leave the mirrored load source set on the MFIOP.  That would give me about
32 gig.  That is much better than the 8 I have now.
Regards,
cjg

Carl J. Galgano
EDI Consulting Services, Inc.
550 Kennesaw Avenue, Suite 800
Marietta, GA  30060
(770) 422-2995 - voice
(419) 730-8212 - fax
mailto:cgalgano@ediconsulting.com
http://www.ediconsulting.com
AS400 EDI, Networking, E-Commerce and Communications Consulting and
Implementation 
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-----Original Message-----
From: midrange-l-bounces@midrange.com
[mailto:midrange-l-bounces@midrange.com] On Behalf Of Douglas Handy
Sent: Monday, February 03, 2003 6:21 AM
To: Midrange Systems Technical Discussion
Subject: Re: Change from mirror to RAID


Carl,

>I have a model 400 that ...  I will be adding a 7117 expansion cabinet 
>to ...

>I would like to RAID all 8 drives in the same RAID set.  Can I do it 
>...?

The model 400, like my 40S with a 7117, does not support RAID on the MFIOP.
Only the drives in the 7117 expansion may be in the RAID set.   You may want
to
consider moving the 2nd paid or 6607's from the MFIOP to the 7117 expansion
since it will hold up to 8 drives.

Leave one pair in the MFIOP to mirror the load source (yielding 4GB
protected), and six drives in the 7117 in a single RAID set (yielding 20GB
protected) for a total capacity of around 24GB.

If you leave the second mirrored pair on the MFIOP, you end up with about
20GB total protected space (4 + 4 + 12).

As far as I can tell from playing with various drive configurations on my
40S, where I currently have twelve 6606 drives, the 6502 will support
anywhere from 4 to 8 drives in a RAID set.  But the actual RAID stripping
seems to be across exactly 4 or 8 drives.  If you establish a RAID set of 6
drives, it will make four of them 75% capacity and the other two 100%
capacity when you look at the actual distribution.

I don't think this has much practical effect on distribution of disk arm
utilization, but it does mean you have a pretty simple way of migrating two
drives from the MFIOP to the 6502 RAID set.  Since the RAID stripping will
be across just four drives whether or not you initially put six drives in
the 7117, just install the 7117 and the four new drives first.  Configure
the RAID set, raising your system to 20GB effective capacity.

Now remove the 3rd & 4th drives on the MFIOP from the configuration.  The
system will migrate the data to the remaining disks (ie, the four new ones
since they have less usage than the first mirrored pair).  Once the data is
transferred, remove the drives, install in the 7117, and add to the RAID
set.  This will raise your effective capacity to 24GB.

Then balance the drive usage with STRASPBAL.

Doug
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