Here's a feature that I'd *love* to see put into ADSM: the ability for ADSM
to pre-stage tape mounts, especially for restore. Here's how it would work:

1) A restore that will require multiple tape mounts is started.

2) ADSM calls for the first n tapes to be mounted. 'n' is defined by an
   ADSM server option called PRESTAGE (I'm making this up). The default
   value for 'n' is '1', which is what we have today. 'n' is limited only
   by the number of available tape drives.

3) As each tape is mounted, ADSM positions it to the first location from
   where data will be read. While the first tape is actually being read,
   the second, third, and so on are mounted, positioned, and ready to be
   read.

4) After the first tape has been read, ADSM can immediately start reading
   the second tape. The first tape is dismounted, and the nth + 1 tape is
   called for.

This should work because ADSM already knows what tapes will be called for
(this must be true because ADSM sorts the list of versions to be restored
by volume).

Such an implementation would speed recovery by almost eliminating the lag
time between tape mount and locate. This would provide the restore
performance benefits of collocation+ without having to incur the overhead
of collocating the data. The actual number of tape mounts would not be
reduced, just the lag time between one tape and the next.

Any comments/thoughts?

Andy Raibeck
Connecticut Mutual
203-987-3521