Block size in NBU

[Neha_K]

Hello All,

Is there any option available to change the block size in NetBackup GUI??

[mph999]

Yes ...

http://www.symantec.com/docs/TECH1724

All the info you need is in here.

[Neha_K]

Hi mph999,

I need to chnage the setting on Windows 2008 platform. IS there any way do do that for netbackup ruuning on windows 2008 as master server.

--Thanks,

Neha

[revarooo]

Exactly the same as that technote, however instead of /usr/openv/netbackup you would put these in the directory %install_path\veritas\netbackup  (where %install_path is where you installed NetBackup)

[sksujeet]

here is the TN for windows

http://www.symantec.com/docs/TECH18422

Make sure you test the backups to see what settings suits you, you might need to play a bit.

[mph999]

The settings go on the media servers ...

[Marianne]

You forgot to tell us NBU version?
There are different defaults and options in the different NBU versions.

We don't change block size in NBU - we change the buffer size to match tape or disk block size.

Defaults and recommendations can be found in the relevant Performance Tuning doc:

Symantec NetBackup™ 7.0 - 7.1 Backup Planning and Performance Tuning Guide: 
http://www.symantec.com/docs/DOC4483

Updated NetBackup Backup Planning and Performance Tuning Guide for Release 7.5 and Release 7.6

[Neha_K]

Hi Marianne,

NBU version is 7.6.

Master server is windows 2008 platform. My master server is acting as media server as well,

there is no size_data_buffer available inm the following path:

<INSTALL_PATH>\NetBackup\db\config

Do i need to create a file? If yes, how do i do it and set the required block size?

In one of the links on symantec forums, its mentioned that i need to create a file on the above location, add the desired values in the multiples of 1024 and need to ensure there is no extension after saving the file. I am bit confused as i am very new to NBU.

I also tried one more thing that is, in host properties>> clients>> Client properties>>windows client >> client settings>>communication buffer size.

the default value is 128 kb. 

i changed it to 64kb. i took a backup to tape library and the throughput and time taken for both the cases (64k and 128k) was the same. Is this a ormal behaviour with NBU?

is this the write procedure to change the block size?? 

Need a resolution at the earliest :(

I would be really great if you can guide me through this. 

Thanks in advance!!

[revarooo]

The question is, why do you want to do this?

[Neha_K]

To measure throughput performance numbers.

[mph999]

<INSTALL_PATH>\NetBackup\db\config

Do i need to create a file? If yes, how do i do it and set the required block size?

In one of the links on symantec forums, its mentioned that i need to create a file on the above location, add the desired values in the multiples of 1024 and need to ensure there is no extension after saving the file. I am bit confused as i am very new to NBU.

Yes, in the dir you create files like this:

SIZE_DATA_BUFFERS (262144)

NUMBER_DATA_BUFFERS (128)

The numbers in () are suggested starting values, so SIZE_DATA_BUFFERS would contain only 262144 and NUMBER_DATA_BUFFERS would contain only 128.

262144 is divisable by 1024, 262144/1024 = 256, so this would be a block size og 256k

Be careful on windows, that when you create the files, they are called only <filename> NOT <filename>.txt   (eg, we do not want ant file extension /suffix)

Windows has a habit of adding suffix only files, and somethimes this is hidden so cannot easily be seen.

No restarts are required for this, the vaules are picked up when a new backup starts.

I do not recommend playing around with the net buffer size, at least not yet until the size/ number data buffers are sorted out, too many changes makes things confusing, and just because they are settings that can be changed, does not mean they should be changed.

[Neha_K]

Thanks for your reply mph999!

i just googled around a bit more, and i found out that if size_dat_buffer is not present in <INSTALL_PATH>\NetBackup\db\config   path then in that case then the default size is 65536 .

so according to the example that ypu gave above, that comes upto 64k of default size..right?

if i need to set the block size to 1024 then the file size should be 1048576..correct?

and one more thing, do i just need to create a folder with size_data_buffers (1048576) as the name?? 

if i need to follow the method mentioned by you, then what about the other setting that i changed:

in host properties>> clients>> Client properties>>windows client >> client settings>>communication buffer size.

the default value is 128 kb. 

is this the other way around??

Need help in understanding this please.

[Marianne]

There is no 'quick solution' for performance tuning.

Download the NBU 7.6 pdf from here: http://www.symantec.com/docs/DOC7449 

Before you change anything, firstly check what is existing (default) buffer sizes and numbers and the effect it currently has on backups.

In the above doc, you will see that you need bptm log on media server(s).
This log folder does not exist by default. 
Create it under ...\netbackup\logs.

After next set of backups, open the bptm log file.
At the beginning of each job, you will see entries similar to this :
(extract from p.129 of the pdf):

12:02:55 [28551] <2> io_init: using 65536 data buffer size
.....
12:02:55 [28551] <2> io_init: using 8 data buffers

To see the effect of these buffer settings, find the following at the end of each backup job:

... waited for empty buffer ....
or
... waited for full buffer ....

Learn in this guide how to interpret results seen in bptm log.

If media server is waiting for full buffers, then increasing SIZE_DATA_BUFFERS will just make matters worse.

Increasing network buffers or number of data buffers MAY improve backup performance, but the problem may be with disk read speed on the client(s). 

The same doc will tell you how to use bpbkar on clients to test disk read performance.

Again - take your time. Read through the doc.
Do not make changes in a hurry.
Understand (with the help of this doc) the path of data flow and how to test and tune each component.

Good luck!

[mph999 · Accepted solution]

Yes the default is 64k

(1)

if i need to set the block size to 1024 then the file size should be 1048576..correct?

Do not set the buffer size that high, for most cases 262144 turns out to be a good value.

(2)

and one more thing, do i just need to create a folder with size_data_buffers (1048576) as the name?? 

No, in ...netbackup\db\config you create a file with the name SIZE_DATA_BUFFERS and in that file you put the value, eg 262144

(3)

As I mentioned, do not worry about net buffer size at least yet, they is a chance it won't need to be changed

[revarooo]

changing the values won't measure performance, it may change performance (for better or worse).

What performance speeds are you currently getting and to what backend storage?
 

[Neha_K]

Thanks Marianne...your post and the document you provided was of great help. Thanks  again!!

Cheers!!

[Neha_K]

Thanks a bunch mph999 !!

Your explainition was really simple. It made my life easier. I tried the steps that you mentioned and i could measure the different throughput for back-ups taken for different parameters set.

Thanks a again!!

Cheers!!

Neha

[Neha_K]

hey revaroo,

i needed to examine different throughput rates (if any) for different block size for NBU. for default block size of 64k, the performance was 41.88 mb/sec for 100 gb data back-up.

--Neha