De-duplication speeds

[cegedimit]

Hi, we are still evaluating BE 2010 R3 and so far have had limited success.

We have created several smaller jobs for difference device types. After encountering multiple errors we have now disabled GRT and use of VSphere where possible as it was too inconsistent.

At the moment if i backup direct to tape then everything is scuccessful and i can get speeds of:

Full backup selection list 1:  1,697 MB/Min 

Full backup selection list 2:  1,978 MB/Min

Full backup selection list 3:  3,865 MB/Min

Full backup selection list 4:  2,356 MB/Min

We have a dedupe folder setup which last updated 4 days ago. I changed the job destinations to go to the dedupe folder rather than tape and got the following speeds:

Full backup selection list 1:  607 MB/Min

Full backup selection list 2:  349 MB/Min

Full backup selection list 3:  558 MB/Min

Full backup selection list 4:  1,027 MB/Min

As you can see this is considerably longer. Is this expected behaviour ? Should using a dedupe folder result in such slower tests ? Is there anyway we can improve this?

For reference, the server originally had 8GB RAM, this has now been doubled as there were a lot of paging and memory issue when running dedupe. The Spec now is:  Windows 2008 R2, 16GB RAM, 9TB Disk Space (7.2k SAS, 6 x 2TB, RAID 5)

[AmolB]

Dedup is designed to save space NOT time. When you target a backup to Tape or Disk there is not 

much of data processing and hence you get better job rate but with dedup there is a lot which happens

in the background which is time consuming.

[CraigV]

7.2K SAS drives won't give you much speed, which can explain why your speed to disk is so slow.

Try a normal backup job and see what sort of speed you get vs. to tape. Don't compare the dedupe backup with the normal B2D due to the nature of what it does during the dedupe process.

[cegedimit]

Thanks both. Agree regarding disks, only option due to size though im afraid. The disk queues dont seem to be getting hammered. I will try a backup to disk to compare and see if it sheds any light on it.

Is there any way we can fine tune / improve dedupe ? I appreciate from your post it does a lot more but are there and do's and dont's in order to get the best speed possible ?

[Sush---]

This may be of some small help

"Any real time scanning the deduplication folder will have some impact on the performance of the deduplication folder."

abstract from " http://www.symantec.com/docs/TECH129606 "

Thanks,

-Sush...