Hello all,

We are investigating replacing our old backup systems with TSM.

We don't want to give up storing away a complete snapshot of
our systems off site every few months, over time maybe reusing
the off site tapes so that we finally save a snapshot a year.

I think that the most logical way to accomplish this with TSM
is to do a complete export like
export server filedata=allactive ...

I have played with it with a smaller data set, 100 gigs or
so, and it seems to work pretty fine. But I have no idea what
will happen when we have a lot of data.

We estimate a filedata=allactive export to about 10 TB (and
somewhere between 30 million and 100 million files, that
numbers is yet unknown).

Given LTO 3 with an maximum data speed of 50 MB/s uncompressed,
a moderate guess (I hope) for the data transfer rate would be
30 MB/s, which would give 93 hours to write it down. Given that
a tape has a capacity of 400 GB uncompressed, it would take
at the most 25 tapes.

We would obviously want to be able to use the backup server
as usual while doing the export.

I have seen concerns about that the export mechanism would
easily bail out at smaller problems, and maybe other issues
with it, that make people avoid using it even for smaller
amounts of data. If this (still?) is true, doing a 74 hour
multi tape export may just not be practical.

Is the above feasible at all?
Is anyone doing this?
Are there any other comments or ideas on the above?

Thanks for sharing your knowledge and experience!

Ragnar Sundblad
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Department for Numerical Analysis and Computer Science
Royal Institute of Technology
Stockholm, Sweden