Steve Gremban writes,
Question #2 has to do with Direct Access Restore which is something Netapp is working on with the NDMP standards group. It allows you to jump directly to the position on the media where a file is located. Right now a restore will have to read sequentially from the beginning of a dump to the position of the desired file.
Actually, the NDMP standard has specified DAR since the outset of v2; NetApp has added DAR to Guinness/6.0. We backup software ("NDMP client") vendors also incorporate rather hefty logic to support DAR in our products. DAR capability exacts a price from users, too, in terms of additional disk space used to store the position of each file, each time it's backed up.
A few random points you might find useful: . NetApp's DAR implementation can recover up to about 1,000 files in a single operation. . ONTAP's NDMP restore logic always reads header & directory data from the first tape of the backup. Then, in concert with the NDMP client, it requests the tape -- if not the one in the drive -- needed to recover the first file in the backup data stream. . Instead of reading & examining each block, as is done in the non-DAR selective recovery case, the tape agent (NDMP mover) uses "space block" operations to position the tape to the tape block in which each requested file begins. It iterates this (swap tapes if req'd, position to next file, recover file) operation until all requested files are recovered.
Best, Jim