We have ADSM running on an IBM RS6000 with a tape robot. We're using this as a hierarchical storage manager (HSM) for user data and for netapp backups. I have written what is essentially a modified rsh that we run on this RS6000. It fires up a dump on the netapp using the rsh service, and the dump writes to stdout. The modified rsh copies the dump output to disk on the RS6000, breaking it up into separate 1G files. (It would have been simpler to just use rsh and pipe it into "split", but it was more amusing to hack rsh.) ADSM is configured to automatically migrate these files to the tape robot. The HSM filesystem gives the illusion that all these files are on disk, but what is actually on disk is just a "stub" file and the real file is on tape.
I break the dump into 1G files because it has to fit in the disk cache in order to be migrated to or from tape. We have allocated a 5G disk cache for the HSM filesystem where we put the netapp dumps. So 1G seems to be a nice, safe, manageable, file size.
We restore with this command.
cat dumpfile.* | rsh toaster 'restore -rf - ...'
This works because cat sequentially opens each file, reads it, and closes it. Each file is migrated to disk when cat reads it, and the disk space is recovered when cat closes the file.
I'm thinking of writing a modified cat that pre-reads the next file to force its migration to disk. That way while I'm writing a file to restore, the tape robot can migrate the next file to disk. When I need the next file, it will already be there, speeding up things dramatically.
ADSM has its own internal backup system and our netapp dump files look just like ordinary data to ADSM. So ADSM backs up our backup files. This is good because if a tape in the robot goes bad and we lose just one 1G file, it would make the entire dump useless.
We can't leave dumps in the HSM filesystem indefinitely because we don't want to fill all the tapes in the robot with netapp dumps. Whenever we delete a dump, ADSM recovers the tape space. So our dumps are good for disaster recovery, but they don't go back very far. I didn't set up ADSM so I don't know how far back the ADSM backups go before that tape space is also recovered.
Steve Losen scl@virginia.edu phone: 804-924-0640
University of Virginia ITC Unix Support