Dave
We had a look at the DEC DLT towers for using them for Legato and AFS backup.
After a detailed discusseion with one of the DEC guys in product
support, we ame to the conclusion that it would be quite possible to
combine the afs3.4 butc callout facilities and Legato Meda and Robot manager.
But you have to be sensible aabout this and have realistic expectations.
1) dump is no problem, but one has to find a way to correlate AFS
tape-labelling and numbering system with Legato's and the organisations
external tape store
2) savedb ditto
3) readlabel cannnot easily be suported because the essence of the
command is that one doesn't know the label of a given tape so how would
one ask the robot to load the tape?
4) scan tape ditto
5) writelabel ditto
6) restoredb must also be a manual operation, you do this when you lost
your AFS backup database, so who would know the ID of the Ubik_db_dump
tape to load. This must be a manual operation (get the last Ubik_db_dump)
7) restore can after some work probably made to work if one first
determines the tape needed and load them in the tower (probably
ejecting other tapes)
A tricky one and one that you want to work is appendump. Our
incrementals are fairly short so we want to place several incrementals
on one tape, but.....
If you go through the motions you find that when the callout asks for
appenddump so and so, you have to load the "the last tape used before
for this series of incrementals" neither the ID passed to the callout
on appendump, or the fact that others use the same drive since the last
incremental, so "yesterday's" tape is not in the drive anymore, are helpfull
Since all problems in IT are solved by adding one additional layer of
indirection, that what I think is necessary. During a series of
incrementals, maintain a list of tape-ids (Legato's media managar
id"s?) used and from that list load the last. If you lose this list
every now and then is not a real problem as AFS backup's appenddump
would be happy with a fresh tape in that case. You need to register the
fact for later restores.
So we will, after we have organised ourselves after the
re-organisation, first try a single drive DLT and then a robot. Only
when it have proven it works, we will purchase one.
Have fun
Joop Verdoes
