Re: BRMS and Parallel Backup

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
> >
> >
> > --

> --