RE: Change from mirror to RAID -- MIDRANGE-L

Douglas,

Do what you said will take way to long.  Here are the steps I would take;
1. Stop mirroring on all drives.  This will double your capacity.
2. Remove the 3rd and 4th drives from the ASP.
3. Physically move the 3rd and 4th drives to the 7117 and all the new
drives.
4. Build a raid set on the 6102 including all the drives.
5. Add the newly configured drives / raid set to the ASP.
6. Start mirroring back up on the 1st and 2nd drives.
7. The system is now available for use and you can start your ASP balancing
in the background.

Douglas is correct in stating that the MFIOP on a model 400 cannot be
RAIDED.  I would/do mirror the load source and raid the 6502.  Raid striping
is either 4 or 8 drives so you will see 4 drives with less capacity and the
2 remaining drives at full capacity.

Trying to add drives to an existing raid set that is part of the ASP can
take 24+ hours on a model 400.  Yet it is only minutes to build a raid set
on drives that are not in an ASP.  If you ever add drives to the raid set,
it is best to stop the raid set, add the drives, then rebuild the raid set.

Christopher K. Bipes      mailto:Chris.Bipes@Cross-Check.com
Operations & Network Mgr  mailto:Chris_Bipes@Yahoo.com
CrossCheck, Inc.          http://www.cross-check.com
6119 State Farm Drive     Phone: 707 586-0551 x 1102
Rohnert Park CA  94928    Fax: 707 586-1884



-----Original Message-----
From: Douglas Handy [mailto:dhandy1@bellsouth.net]
Sent: Monday, February 03, 2003 3:21 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.