Re: Hot-swapping disks of different size in a RAID set

First off, the procedure that John condenses is correct and in my view and fraught with so much danger I would never consider it. Kirk made a comment about RAID rebuild, yep that'll take a few minutes, lots of 'em.....

Then there's a question. To add an HSL loop to the box requires down time to potentially add the HSL adapter and connect the HSL loop. A used 0595 and IOP/RAID card is very inexpensive. (Maintenance, maybe notsomuch). Total time to add the loop about 45 minutes. No drop of the RAID set, not copying data, way lower risk. What am I missing?

Jim Oberholtzer
CEO/Chief Technical Architect
Agile Technology Architects, LLC


On 7/15/2011 2:57 PM, Kirk Goins wrote:

Be prepared for a very long RAID build on that size drive... especially
since there will be data on the drives.

On Fri, Jul 15, 2011 at 12:38 PM, John Jones<chianime@xxxxxxxxx> wrote:

> DrFranken, so is what you're describing the following:
> 1. GO SAVE/21
> 2. End RAID5 *At this point the system has no protection from disk
> failures*
> 3. Disk-by-disk, logically remove each 70GB disk via SST, replace it with a
> 280GB, and add the 280GB to the ASP
> 4. Do a load source migration type of trick to move the load source
> 5. Re-establish RAID5 to gain protection from disk failure
> 6. Probably do some form of STRASPBAL when done
>
> Re: Item 5: IDK about 525s but on our Power5+ 570 we IPL one V6R1 LPAR from
> 280GB SCSI disks (4329s on a 2780).
>
> On Fri, Jul 15, 2011 at 1:54 PM, DrFranken<midrange@xxxxxxxxxxxx> wrote:
>

> > Yes. (this is totally crazy)
> >
> > You will need to take the system down during part of this at least.
> >
> > 1) You cannot use a 140 or 280GB Drive to replace a 70GB drive in a RAID
> > set. Even if you could (as some vendors allow) it would be treated as a
> > 70GB drive.
> >
> > 2) You cannot replace the Load Source disk unit without an IPL in any

> case.

> >
> > 3) Replacing drives in the manner of which you speak can mostly be done
> > live but YOU ARE EXPOSED during 100% of the swapping. A disk failure
> > between the beginning of 'STOP RAID' to the completion of 'START RAID'
> > at the end means *RELOAD. As a consequence a SAVE 21 (maybe 2?) before
> > you start is mandatory and if the system is running production you still
> > could lose that. It can work but not without at least one IPL PER DISK
> > PULL. (More than one disk could be pulled at a time.)
> >
> > 4) NOte that if you are on V7R1 the disks can be completely removed
> > without an IPL (except the Load Source.)
> >
> > 5) I do not believe you can IPL from a 280GB Disk unit on a 525. There
> > was a restriction there and I*think* it's still there for SCSI drives.
> > So 140 GB units are best choice.
> >
> > - Larry 'DrFranken' Bolhuis
> >
> > On 7/15/2011 2:03 PM, Johnny Lee Lenhart wrote:

> > > Hi there:
> > >
> > > We have a 9406-525 with 8 4327 (70 GB) disk drives in a single RAID

> set.

> > > The drives are in the system enclosure and there are no additional

> slots

> > > available. We are at 85% DASD utilization.
> > >
> > > We have an idea for increasing our DASD capacity without taking our
> > > system down. Our thought is that we could fail one of the 4327 drives,
> > > replace it with a 4328 (140 GB) or 4329 (280 GB) and let the RAID
> > > controller rebuild it, and that we could do this one-by-one until we
> > > have replaced all of the drives, thus doubling or tripling our current
> > > DASD.
> > >
> > > Is this totally crazy? One person I've talked with suggested that you
> > > can't have mixed sized disks in one RAID array, but our network admin
> > > thinks we did have this in an 810 we used to run. Someone else thought
> > > that we might have issues increasing our DASD capacity without
> > > increasing disk arms, but our current performance metrics don't seem to
> > > support that concern. At any rate, we are willing to take that risk.
> > > Our main interest right now is answering the question about whether or
> > > not this disk-at-a-time replacement into the same RAID array is
> > > possible. We really can't afford to have our system down for the time
> > > it would take to do the backup/change disks/restore method.
> > >
> > > Thoughts?
> > >
> > > Thanks,
> > >
> > > Johnny Lee Lenhart
> > > Sr. Technical Specialist
> > > Brattleboro Memorial
> > > Hospital
> > > Brattleboro, Vermont USA