NDMP Backup - Size Issue

[gpthalverton]

We have Backup Exec 2010R3 running NDMP backup from a Netapp FAS2050 (Ontap 7.3.4) to a SAN-attached tape library.  We use Netapp Virtual Storage Console (SMVI) to create daily snapshots of the target volume and use BE to backup the most recent snapshot using the following path (setup in the backup job selection):

//NetappNDMPServer/vol/vmfsdatastore1/.snapshot/smvi_DailySnap_recent/

The volume shows as using 477GB (including snapshots) on the Netapp, but the Byte Count on the NDMP backup to tape is 1084GB.  Trouble is we have 2 similar volumes to backup with NDMP and now we are having difficulty fitting both volumes onto 2 x LTO4 tapes.

Sorry if this is a stupid question but please can someone help me understand why the Byte Count on the NDMP backup is so much higher than the total data usage on the volume?  (We currently have 60% dedupe on the Netapp volume, are we perhaps losing the dedupe when dumping the volume to tape with NDMP?  I haven't seen anything written about this from Netapp.)

Any advice gratefully received.  Thanks.

Mark

[scottgelb · Accepted solution]

You are correct.  NDMP rehydrates the data.  So the volume has 500GB of data that deduplicates to 250GB, it takes 250GB on disk but hydrates to 500GB on tape.  There is no dedup to tape from the FAS controller.  If you want dedup to tape then you use SMTape (SnapMirror to Tape) but that only supports full backups and full restores of the volume so has some limitations.

[gpthalverton]

@Scott - kudos to you, good to know!

Would be good if NetApp pointed this out more clearly, didn't see any mention of this in any manuals/etc.  Because we are dumping vmfs datastores this is fairly limited anyhow (dumps the whole lun and not individual vm snapshots), so we may look at SMTape as a possible alternative, thanks for the tip!

Mark

[scottgelb]

Good point... VMFS won't have file restore either...all or nothing with the VMDK... but you do have VMDK granular restore.  If you use SMTape, then you have to restore all VMDKs in the volume and have enough aggregate space to restore the entire volume to grab the VMDK you want then destroy that volume.  It will save tape space though.

Also...starting with 8.0, SMTape allows you to specify a snapshot then the dump takes the volume from that snapshot backwards... for example if you have 10 snapshots and specify snapshot 5... then you will backup 5-10 to tape instead of 1-10.  Down the road hopefully we'll see incremental backup and single object restore added but no guarantees or road map I know of.