Well the thing is, there isn't really any rehydration going on.  You're just reading at the file level and not getting any of the benefits of deduplication that you might anticipate -- you are really backing up all 1.58TB and not 813Gb. 

There's very little performance impact from reading deduped volumes.

From: Scott Eno <s.eno@me.com>
To: Fred Grieco <fredgrieco@yahoo.com>
Cc: Scott Eno <s.eno@me.com>; Toasters <toasters@teaparty.net>
Sent: Friday, December 21, 2012 9:37 AM
Subject: Re: question about NDMP dumps

Thanks for the response.

This may be a silly question, but where/what is the bottleneck in the re-hydration process?  The CPU on the controller?  The disks?

I don't really see extra CPU activity that matches the time of the dump.


On Dec 21, 2012, at 9:30 AM, Fred Grieco <fredgrieco@yahoo.com> wrote:

Yes.  Dedupe is at the block level, but NDMP is a file level backup.  So an NDMP-based backup is backing up "hydrated" file data.  A block level backup (really only snapvault/snapmirror are available for Netapp) would be faster.  But then again, there are efficiencies with compression during most backups...


From: Scott Eno <s.eno@me.com>
To: Toasters <toasters@teaparty.net>
Sent: Friday, December 21, 2012 9:12 AM
Subject: question about NDMP dumps

In investigating why an NDMP dump over 10GbE isn't going as fast as it seems it should, a question arose.  Does the data being dumped via netbackup to a data domain device, 1.58TB deduped down to 813GB, have to get re-hydrated as the dump proceeds?  And, if so, would that impact the speed of the dump?
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