"ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU> wrote on 03/24/2011
04:08:28 PM:

> Couldn't you create a copypool into the same DD device class?  If you
had
> 2 pools in the same DD

> And this *shouldn't* cost anything
> except for the I/O of TSM creating the local copypool.

Have been thinking about this.  We are counting on getting rid of
the I/O to the copy pool, as well as the db meta-data associated
to it.  So I don't think this is where we want to go.

> We had a compression card failure in 2007 that caused corrupt data to be
> saved to disk (different vendor)  The 2-pool model saved us that day.
> Ever since then, I've been hesitant on the one-pool model, although I
> haven't heard of any data corruption issues lately.

It's also not just one pool, but one disk system.  With tape you loose
individual pieces of media.  A hdwr or os bug could loose all your
backups,
and that's kind of scary.

In stead of two pools (primary and copy) I've been thinking of
DD snapshots.  The problem with snapshots is that they are over the entire
DD filesystem, and, that there is no way to revert the entire filesystem
back to a snapshot (you can only copy stuff out of a snap). A snapshot
might be useful for a TSM database backup, but not for a filepool of
all your backups.



Rick






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