Jim Ward wrote:
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
The DAR specification in v2 was too ambiguous and nobody used it. The implementations that are just becoming available are based on extensive work done on DAR in v4.
Once Guinness is released there will be a way in Veritas to capture the DAR positioning info during backup so that in a future release of Netbackup you will be able to use DAR to restore it.
I'm assuming from Jim's message that Workstation Solutions has DAR implemented for Quickrestore and it's interoperable with a Netapp running Guinness.
-Steve gremban@ti.com