ADSM-L

Caching and backing up.

1999-09-27 11:51:01
Subject: Caching and backing up.
From: "Allen S. Rout" <asr AT NERSP.NERDC.UFL DOT EDU>
Date: Mon, 27 Sep 1999 11:51:01 -0400
I know that a disk pool with caching enabled lets you restore data that has
been "theoretically migrated" from disk, and only overwrites old data as space
becomes necessary.

Is ADSM smart enough to take data from the cache in BACKUP STGPOOL operations?


For example,
-- Postulated scenario --
DISK, a 10G stgpool, devclass DISK
DISK, a 10G stgpool, devclass DISK

TAPE, a "sufficiently large (*)" tape stgpool, devclass mytape

COPY, a sufficiently large copy pool, devclass mytape


Since I perfectly adjusted my tape pool for the load, an incremental is
precisely 10G.

I accidentally start migration early, before I've backed up.  I halt it with
5G migrated.

----
Given this scenario, will I find that:
Given this scenario, will I find that:

A: ( nirvana )
  if I BACKUP STGPOOL DISK COPY, I will back up 10 G to the copy pool, and
  find that there is nothing left in TAPE that needs to be backed up.

B: ( convenient )
  if I BACKUP STGPOOL DISK COPY, I will back up 5G, and then on issuing the
  BACKUP STGPOOL TAPE COPY, ADSM will pull all the file images off the cached
  copies in DISK, avoiding a tape mount.

C: ( no effect )
  if I BACKUP STGPOOL DISK COPY, I will back up 5G to the copy pool, and a
  subsequent BACKUP STGPOOL TAPE COPY will generate a tape mount.


If someone has already walked this path, let me know.  Else, I'll set it up
myself and see what happens.


Allen S. Rout



(*) Gotta love Bently motorcars.
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