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Re: BRMS and Parallel Backup



fixed

Jim, could you elaborate on the duptap portion of this. Let's say you have
a tap04 and a tap05. Which would you pick to do the duptap from?? Would
it matter on which one had the least amount of data on it, didn't have the
boot code or ??

On Mon, Nov 5, 2012 at 1:54 PM, Jim Oberholtzer <midrangel@xxxxxxxxxxxxxxxxx
wrote:

BRMS is not the issue here. It's where the data is. BRMS is using the
standard save/restore functions to accomplish the parallel saves. The
real issue is that objects are written to two devices at a time.
Therefore, a restore with a single device must do one of two things. A)
It has to swap tapes as it lays down part of the data from tape 1 and
then the next series of data is on tape 2. So it goes back and forth
until the restore is is done. If there are two devices then the system
reads 1 then reads 2 then reads 1, and so on. With a single device the
same process happens, but the tapes have to be unmounted and then
remounted. Or B) it has to be able to merge the data on tape 1 with the
data on tape 2 before doing the restore. IBM i does not currently offer
option B as far as I know at this point.

It comes down to a short but very important point I make in every user
group session I do regarding BRMS or any type of recovery. That is:
Plan the recovery first. Then build the back up to support the recovery
plan. Too often the recovery plan comes as the result of what type of
backups you have, that almost always fails at some level in a recovery.

If you have the space, create a virtual tape device and one virtual
tape. DUPTAP one of the tapes into the virtual tape image. Now you can
use the virtual tape and the physical tape together in a dual device
environment.

BRMS nor IBM i Save/Restore provide the function to speed up saves, and
restores, but you always have to understand the ramifications of the
functions.

Jim Oberholtzer
Chief Technical Architect
Agile Technology Architects


On 11/5/2012 11:23 AM, Graap, Kenneth wrote:
Several months ago I performed a recovery test for a client in the same
situation.
We wound up using my tape library to get the job done, but it was at
best a very ugly process.
I figured it would be "ugly" ... I was hoping that BRMS would help me a
bit more in a situation like this though.

BRMS does let you adjust the tape resources to be used for 'Parallel
Saves' ... I had changed it to MIN(1) MAX(1) ... hoping that this might
affect how the restore would be done. BRMS let me do this too without
sending me a nasty message!

I also expected having to load and reload a couple tapes many times, but
the tape library could have handled this for me.

Anyway, this was just a test. I have had another tape drive on order and
it should arrive in a few days. I just wanted to know if in an emergency
where I lost one of my tape drives at my remote site, that I could at least
"limp along" with one.

Based on the feedback I got to my question, it doesn't look like that's
a very good option...

And by the way... The new tape drive I ordered has 2 drives in it, so my
recovery site will always have one extra drive available, just in case.

Reply or Forwarded mail from: Kenneth E Graap


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