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How data buffer size and buffer number effect the Netbackup backup and restore performance?

Created: 19 Dec 2011 • Updated: 21 Dec 2011 | 6 comments
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Lately we are having a performance issue in our Widnow server. After looked into details, we found we had smaller data buffer size and buffer number in our Windows serve compare to our HP-UX server.

Can someone please help me with my confusings?

1. Does the data buffer size and buffer number effect the backup and restore performace dymantically? 

    It looks the backup performance is almost 10 times faster in our HP UX server than in our Window server.

        HP-UX 11.31, version: 7.1.02, data buffer size: 262144, buffer number: 64

        Windows 2008, 64bit, version:, data beffer size: 65536, buffer number: 12

2. How can we determine what is the best data buffer size and buffer number in our enviornment?

3. How can we set the data buffer size and buffer number in Window/Unix server?

4. Should we make the changes on media server only or both media server and client?



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Will Restore's picture

better to read through the technote


how they work and how to configure them

Will Restore -- where there is a Will there is a way

Nicolai's picture

1: Yes it does - it the #1 tweak for Netbackup. With today's tape drive using a 256K bloksize is a must do. Else you can't keep tape drives streaming. Frequently start/stop operation (aka. shoe shining) increase wear and cause slow tranfer rates. Personally I use 262144 (256K) bloksize and 256 in NUMBER_DATA_BUFFERS. I use 512 for NUMBER_DATA_BUFFERS_RESTORE.

2: By trying different settings methodical. My experince show 256K blocksize is the preffered value (don't forget to run restre test of you change settings).

3: See Wrobbins post or the Netbackup Performance and tuning guide

4: Buffer settings are media server only.

See also:

Assumption is the mother of all mess ups.

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FelixZhou's picture

Hi Nicolai,

Your message helps a lot. After quickly checked the docs you mentioned, i didn't find anywhere mentioned how to make these buffer paramater changes on Windows platform. can you clarify further?

Nicolai's picture

It's page 125 in the Netbackup Symantec NetBackup™ 7.0 - 7.1 Backup Planning and Performance Tuning Guide.

Assumption is the mother of all mess ups.

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

Mark_Solutions's picture


On your Media Servers under \program files\veritas\netbackup\db\ create (if it does not already exist) a folder named "config" - by default this folder only exists on a Master Server.

In that folder create your buffer files, they are case sensitive and do not have a file extention so make sure your Windows Explorer is not hiding extensions for know file types otherwise they may end up with a .txt on the end.

From my experience on Windows and using LTO4 or LTO5 drives and also backing up to disk the following work really well as long as Windows paging is also tuned:

SIZE_DATA_BUFFERS with a value of 262144

NUMBER_DATA_BUFFERS with a value of 32

SIZE_DATA_BUFFERS_DISK with a value of 1048576

NUMBER_DATA_BUFFERS_DISK with a value of 32

To tune your paging use the following registry keys (need a reboot) - create them if not already there:

HKLM\System\CurrentControlSet\Control\Session Manager\Memory Management\

DWORD - PoolUsageMaximum  - Decimal value of 40

DWORD - PagedPoolSize Hex value of FFFFFFFF (this is 8 x F)

Hope this helps

Authorised Symantec Consultant . Expert Partner.

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FelixZhou's picture

you guys are great. thanks.

I think now i have some ideas and i will give it a try.