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
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
Steve Gremban writes,
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.
NDMP v2 and v3 both specify DAR. The DAR semantics are basically unchanged between these versions of the spec. (I don't anticipate any DAR change in v4, either, other than, perhaps, tighter language.) NetApp implemented DAR in ONTAP releases prior to Guinness but it didn't work reliably, thus no one used it. (We tried.) Those ONTAP 5 releases do, however, produce file position information that are valid; so, any backup vendor that saves file positions generated at ONTAP >=5 will be able to use them for DAR at ONTAP >=6. It's important to keep in mind that there were no NDMP protocol changes to support ONTAP 6; rather, it implements both NDMP v2 and v3 and supports DAR, reliably, after negotiating either protocol version. Meanwhile, the NDMP WG continues to hash out the v4 definition.
I'm assuming from Jim's message that Workstation Solutions has DAR implemented for Quickrestore and it's interoperable with a Netapp running Guinness.
Just so: QR supports DAR with ONTAP 6, even for filer backups performed with QR at ONTAP 5.
Best, Jim
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Jim Ward -
Steve Gremban