Re: Where do I learn about SAN backup?

Okay, this is making some more sense.

When you IPL the flash copy LPAR, everything is just a pointer to the existing production LPAR (until it changes). If you didn't change a single block of data on production, you'd in effect have nothing but pointers to that data. Until you changed something on the flashed partition.

So you have:

Data that has not been changed on either partition
Original version of data that has since been changed on production
Data that has been changed on the copy partition

And some serious magic that keeps it all in order.

So it would seem that you have to be careful not to touch your production data in the flash copy partition until after you back it up. If you for example cleared a master file and then backed it up on the flash copy, my guess would be it would be as if you cleared it on production and backed it up.

But even so, that's pretty fantastic stuff.

Joe--

<snip>

How does the flash actually work? FM... It does not actually duplicate all of the data! The flash all takes place in the V9000; the iSeries shouldn't know it's even happening! The V9000 creates a bitmap for each block of storage in the production LPAR. This has nothing to do with physical files, records, objects; it's just a block of storage. The Flash LPAR doesn't have any real data in it-- until either the production or flash LPAR changes something.
If the production LPAR updates something, a copy of the affected blocks is duplicated into the flash LPAR, and the bitmap is flagged to indicate that the data in those blocks has been duplicated in the flash copy.
Likewise, when the flash LPAR updates something, the data is duplicated into the flash LPAR before the data is touched-- and the flash copy is updated.
This is how you can have 2 copies of the data-- the flash copy is frozen at the moment the MKSYSCPY runs; the production LPAR can continue to run as normal. Because the system has to check the bitmap before it can access any data, there is some overhead. But this is minimal compared to shutting down an LPAR to do a backup!

Paul E Musselman
PaulMmn@xxxxxxxxxxxxx

.

-----Original Message-----
From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Joe Pluta
Sent: Thursday, August 24, 2017 3:18 PM
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>
Subject: Where do I learn about SAN backup?

I'm hearing that SAN storage allows us to do a very fast "snapshot" of
the system and then backup from that snapshot. It's supposed to make
the backup less intrusive. Is anyone doing something like this?

Thanks in advance!