I'll add a cautionary note here. We do a rotation that we manage ourselves. Mostly because the differential and full backups are a little different. We've got 5 2-bay USB chassis. On 1 drive we have 4 folders for Mon - Thu. The other drive has one folder for the full on Friday. Each Monday we swap the entire chassis.
To do this we need to stop the tape engine, stop the USB device, swap the USB chassis, and restart the tape engine. The tape engine song and dance is needed to close the open pointers to the FSD.
When we connect the new USB chassis we need to go back into the device groups and reassign all the folders to the proper group. It would be nice if the program (R12) would remember that we told it that all the folders on E: are in PGRP0, the folder on F: is in PGRP1 and so on. Instead, each folder is in it's own PGRP. I've tried setting my job destination as any PGRP that has a media from the proper pool to avoid this step but it doesn't seem to work. Someday I'll address this issue with CA.
Other than needing a few minutes of care each Monday morning (and the last Friday of the month for a monthly dump) the FSDs work fine.
The USB chassis are hot swappable. I haven't tried this but suspect it would be a problem since Arcserve keeps file handles open and that's not a good time to swap a drive.
- Joel