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Image CleanUp Process using VTL

mansoor_sheik
Level 6
Certified

Hi All,

I manually expired the image using Catalog window in Netbackup Admin console.( Step:  Just selected the image and clicked Expire.)

But I unable to get  free space in DD( DD is configured as VTL).

I just read the below mentioned article and have a query, Do I need to really issue the below commnad to reclaim the space in DD

https://www-secure.symantec.com/connect/forums/what-image-clean-job-netbackup

bpexpdate -deassignempty -force

28 REPLIES 28

Nicolai
Moderator
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DON'T !!!!! - using multplexing on deduplication devices destory the possibility to do deduplication becuase each backup - when multiplxed - present a new set of unique fingerprint.

The workaround is to define more VTL tape drives and disable MPX:

3 drives with mpx of 4 = 12 streams (using real tape drives)

12 VTL tape drives with MPX of 1 (using VTL drives on deduplication devices).

You will see the deduplication rate rocket if you disable MPX. That means you can have more data on the device.

sdo
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I'll just chip in... MPX on VTL with no dedupe behind is ok.  I have previously used MPX on VTL, and the VTL had hardware compression cards (e.g. similar to what real LTO does) and did not have dedupe, and it all worked fine, and got the same compression rates as real LTO.

And as Nicolai says MPX on VTL with dedupe behind sounds like bad news.

Marianne
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Every single VTL best practice doc that I have seen says that MPX on VTL STU must be set to 1.

Have a look at this Symantec White Paper:

http://eval.symantec.com/mktginfo/enterprise/white_papers/b-whitepaper_using_virtual_tape_libraries_... 

sdo
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Thanks M.  I may be mis-reading it, but that doc doesn't say to not use MPX.  In fact, it seems to imply, in at least two places, times where MPX could be introduced for VTL.  Of course, you are right about getting the levels of MPX right.  We were very careful, and didn't over do it, and had super results with an MPX of 3, as the VTL was capable of sustained ingest at 1200 MB/s - all over a carefully designed/balanced FC SAN configuration.  But, we didn't have dedupe behind.  We only had hardware compression cards to offload the compression work from the main CPUs/servers inside the VTL.

I'm with you on setting MPX to 1 for VTLs, as this is probably best for most sites and most configurations.  Only a few might benefit from a little MPX - but even then, any MPX has complex ramifications for any subsequent duplication to real tape.  In summary, one has to be extremely careful with MPX on VTL.

Marianne
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You are right - the Symantec White Paper does not say this in so many words.

I have with previous VTL encounters asked the VTL vendor for best practice doc.
Each of them without fail said that MPX must be set to 1.

Nicolai
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We are getting off-topic - since Mansoor's VTL is on Data Domain, lets keep to the subject and the recommendation on MPX=1

sdo
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:)    Yes.   Sorry.   MPX of 1 for DD VTL + dedupe.

sdo
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I think my use of MPX on a VTL was probably a limited use case.  The VTLs were EMC EDL 4206 - in what was probably a very specific configuration.  Not suitable for all.

And yes, I also seem to remember seeing other vendor documentation stating that MPX "must" be 1 for their VTLs.

All I wanted to do was to highlight that sometimes (rarely?) that MPX can be used to good effect on a VTL.  But certainly not for the use case for the OP of this thread. 

mansoor_sheik
Level 6
Certified

Hi All,

Thanks. I will work and update on the issue. It may take some time. Here the policy changes require a detailed analysis. I am reading the document to provide the same to client. 
Thanks for throwing some light on the issue.