On Wed, Nov 30, 2011 at 8:16 PM, Allen S. Rout <asr AT ufl DOT edu> wrote:
> How many tapes do you have? Now envision _all_ of them being mounted
> for any restore, even a relatively small one.  That's the end state of
> colloc=no: to a first approximation, every node, every filespace,
> every directory, is smeared across a maximum number of tapes, with no
> tendency to re-group data which is predictably related

Mounting 1000 tapes to restore 20G would not be good. I agree.

> Collocation is about paying, in unused tape space, for efficient
> restores;  I'd suggest you view that as a bargain, not a burden.

Having our tapes extremely under utilized to achieve some kind of
acceptable performance is a burden.

I only see using disk as a solution here. At least for incrementals.
We don't have the time to do extensive micro management to reach a
compromise between unacceptable tape utilization and unacceptable
restore times.

Hans Chr.