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Re: BRMS and Parallel Backup



fixed

Ok, thanks.

On Mon, Nov 5, 2012 at 3:34 PM, Jim Oberholtzer <midrangel@xxxxxxxxxxxxxxxxx
wrote:

I'm not sure it matters which tape you chose to duplicate. The point of
the exercise is to get two devices that Save/Restore can use to do the
recovery. In this scenario (one I only would recommend for extreme
situations since disk arm activity is going to be a potential bottle
neck during the recovery) you have one physical tape drive, and one
virtual. Now Save/Restore can use parallel devices. One side of the
tapes need to be on the virtual and one side of them needs to be
virtual. This also makes the assumption that there is enough space on
the system to allow for the virtual tape.

My preference would be to have the tape that has the start of the LIC
(if this is a full system save) on physical tape so the tape device can
be used to boot from. Still I see real problems because you can't
create the virtual tape device or virtual tape image until you have LIC,
the OS, and QGPL and QUSRSYS loaded on to a system. So until you get
those restored, you still stuck with the tape mount/un-mount activity
until that part's done. Fortunately those libraries are usually
relatively small by comparison to the entire system. You might be
better off in that situation recovering the LIC, OS, QGPL, and QUSRSYS
from distribution media then moving forward from there.

Better to plan the recovery, back up to recovery plan.

Jim Oberholtzer
Chief Technical Architect
Agile Technology Architects


On 11/5/2012 1:17 PM, Jack Kingsley wrote:
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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