Re: Disk RAID/mirroring/hot spares, etc

Jeff,

Your not off your rocker, all good questions.

As to question 1: From IBM:
The January 2006 announcement stated that the new DASD IOA's (*#5737/0648/5776*) would support RAID-6 and these adapters would be supported on V5R3M0, V5R3M5 and V5R4. The #5737 is the IOP based controller supported on models 270, 8XX and 5xx. Feature 5776 specifies no IOP required for i5/OS V5R3M5 or V5R4 on 5xx models. Feature 0648 requires no IOP and is specified for AIX on System i.

If you have those raid controllers you can use RAID-6. You will have to stop RAID in DST (dedicated so an IPL is needed into manual mode) and then restart RAID. The options in DST are particularly obvious, if you need help with screen shots, I can provide them for you. Caution: You will have an unprotected system while the RAID is dropped and rebuilt. Several of my customers with the extra space are utilizing RAID-6 now and it is working great. (V5R4)

As to question 2:
Virtual tape is a great idea for incremental back ups and smaller backups only because of the disk space. If you go that route I would suggest you pull as many of the drives as you feel you need for tape space and move them into an iASP. That will improve your recoverability from the virtual tape and also do a nice job of splitting up I/O etc. As to it being faster or slower, why not just try it temporarily and see? It won't cost you anything to try.

Question 3:
If you can move your applications into an iASP you are already set up for Power/HA and replicating data between disk farms is a great idea for highly available systems. It won't guard against any local disaster, but if you plan to move to an off site replicated system in the future, this would be your first step anyway. So a shorter answer to your question is; it depends on what your long term recovery point/time objectives are and if you are going to replicate to another server somewhere.


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


On 4/15/2010 11:48 AM, Jeff Crosby wrote:

*This message was transferred with a trial version of CommuniGate(r) Pro*
Don't laugh at how naive I am in this.

We have an i5 520 at V6R1, 16 35gb drives, RAIDed in 2 sets of 8.
They are on separate controllers (for sure) and separate buses (I
think). Two 3581 LTO-2 tape drives.

After a great presentation at our LUG the other morning on clearing up
disk space (Thanks, Rob Berendt) I found and removed 146gb of old
performance data from V5R4 that was created when I moved to V6R1.
Coupled with removal of an IXS card last summer, we went from 45% disk
utilization this morning to a current disk utilization if 15%. That's
a lot of room and I came up with some ideas.

1) Could I take 1 drive in each set and make it a hot spare? Each
RAID set would then have 7 drives and I would have 2 hot spares.

2) Virtual tape. Backup to virtual tape, then DUPTAP to physical tape
to lessen the backup window. What I read on virtual tape, though,
leads me to believe it won't be much faster than direct backup to the
physical tape drive, if at all.

3) Here's the one to laugh at. Could I split these disk drives into
separate ASPs (or whatever they would be called) and have one of them
be a mirrored backup of the other? The OS would keep them in sync,
and when I want to do backup, tell it to suspend this mirror, backup
the second ASP onto physical tape, and then resync the mirror?
Therefore there would be no backup window whatsoever, and the tape
backup I created would be identical to what I'm doing now? Including
the SAVSYS done every week? Am I off my rocker here?

Thanks.