NDMP backups wrting data more than the total volume si

[PranavB]

Team !

We have master server running on 7.6.0.1 and facing very weird issue when NDMP backups are backing up data that is more than the size of entire volume.

Below I am going to show one example.

stpnascl4n1> df -h vol9
Filesystem               total       used      avail capacity  Mounted on
/vol/vol9/                18TB       15TB     2872GB      85%  /vol/vol9/
/vol/vol9/.snapshot      778GB       48GB      729GB       6%  /vol/vol9/.snapshot

Attached is the detailed job description shoiwng it backed up 31Tb. This is the issue with many of the volumes of diffrent filers.

One volume is backing up 40Tb when its total size is 11Tb  and I confirm no migrations or change in volume size happened anytime in recent past.

Any advise what could be wrong ?

[SymTerry]

Hello,

From what I am seing df  on a filer, is not an accurate measure of how much space is taken by data. If that data is compressed, and you have diferent types of data being compressed then it will be hard to tell what is truely the size. You might be seeing the decompression of that data when NetBackup gets it.

[Marianne]

You will notice that it is the DUMP command on the filer sending the data to NBU.

So, you may want to ask your NAS vendor about this....

[jim_dalton · Accepted solution]

SIS?

Ie single instance aka dedup? This will reduce the size of data on disk where identical data blocks are present but when you move it off to tape it has to give you the real data without dedup so it will grow and the on-disk benefits of single instance no longer persist. IIRC there is a method for putting the data as-is on tape, but Netbackup isnt it.

Jim

[Andy_Welburn]

To see how much space is actually 'saved' as a consequence of SIS & compression on a NetApp volume have a look at using the -S switch for your df command - NetBackup will 're-hydrate' when backing up so will include the 'used' and 'total-saved' amounts when it backs up.

[PranavB]

Geeks , Is there any possible way to put data of netapp volume as is in Netbackup ?