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Created: 11 Apr 2013 • Updated: 06 Jun 2013 | 7 comments
This issue has been solved. See solution.

Hello House,

I was going through a couple of research works from other colleagues and was given the beolw parameter for Data domain VTL drives/Disk STU buffer but didinot work:


Work's the same way as NUMBER_DATA_BUFFERS. In NBU 5.1 the default buffer size has been raised to 256KB (largest SCSI block size possible). You can however lower that value with SIZE_DATA_BUFFERS_DISK. If NUMBER_BUFFERS_DISK/SIZE_DATA_BUFFERS_DISK doesn't exists values from NUMBER_DATA_BUFFERS/SIZE_DATA_BUFFERS are used.

I have implemented this for Data domain VTL and Disk STU but it is still using the one for LT0 tapes drives.

Could house assist with a way to implement buffer tunning for Data domain VTL/Didls STU  because I have both VTL drives and LT0 drive on the same media servers in y env netbackup

Very grateful for all

Operating Systems:

Comments 7 CommentsJump to latest comment

Yasuhisa Ishikawa's picture

Tuning of these parameters improves data transfer between parent and child bptm. You don't need to mind best values for each device. Better tuning is better for both VTL and LTO.

From my experience of these days, default buffer size(64kB for tape) and 64 buffers marks 250MB/s tranfer in each stream. Default buffer size and 128 buffers is enough for LTO5 and LTO6. I'm not sure how fast the DD VTL is, but I believe it is not so fast as LTO6.

BTW, I prefer to use default buffer size because 128kB(or more) buffer size lead to backup and restore error with some hardware(LTO3 drive of some vendor, for example).

Authorized Symantec Consultant(ASC) Data Protection in Tokyo, Japan

teiva-boy's picture

Depending on the DD model, it far exceeds LTO5/6 speeds.  Upwards of 8600MB/s of ingest.

The benefit of a VTL or disk is that it can go slower than the minimum tape speed as needed or as fast as tape...  DIsk is good, even if it emulates archaic tape...

There is an online portal, save yourself the long hold times. Create ticket online, then call in with ticket # in hand :-) "We backup data to restore, we don't backup data just to back it up."

Yasuhisa Ishikawa's picture


Really? Very Fast...
But, in single stream? I assume this is total transfer of multiple aggregated streams. I have never tested, but it is hard for me to believe such perfomance in single stream with dedup operation.

Authorized Symantec Consultant(ASC) Data Protection in Tokyo, Japan

RamNagalla's picture


Netbackup does not have different buffers for VTL and LTO,  because Netbackup does not aware if that is a Virtual tape or Pyisical.

we have one global parametner and 3 specific parametners when comming to Number data buffers






see the below T/N for more details about this.

so you have option to set different for disk and tape.. but not for VLT and LTO.

Nicolai's picture

You need to create the NUMBER_DATA_BUFFERS{_DISK} /SIZE_DATA_BUFFERS{_DISK} for each media server. 

The data domains - are you using the VTL or Open Storage option ?

Assumption is the mother of all mess ups.

If this post answered your'e qustion -  Please mark as a soloution.

Marianne's picture

I do realize that this thread is almost a month old and seem to have been 'abandoned'.

 Nagalla pointed out correctly:
"Netbackup does not have different buffers for VTL and LTO"
" you have option to set different for disk and tape.. but not for VLT and LTO."
So, you are left with buffer sizes for tape.

Supporting Storage Foundation and VCS on Unix and Windows as well as NetBackup on Unix and Windows
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