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How to adjust the FlashBackup read buffer for clients.

Created: 16 Apr 2009 • Updated: 04 Aug 2009 | 10 comments
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Pravs's picture
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I was working with a customer where he was just worried about his flashbackup Backup performance. Here is a quick tip to increase read and write buffer.

How to adjust the FlashBackup read buffer for clients

  1. Create the following touch file on each client:

    UNIX/Solaris: /usr/openv/netbackup/FBU_READBLKS

  2. Enter the desired values in the FBU_READBLKS file, as follows:

    On the first line of the file, enter an integer value for the read buffer size in blocks for full backups and/or enter the read buffer size in blocks for incremental backups. The default is to read the raw partition in 256 Blocks (131072 bytes/128 KB) during full backups and in 64 blocks (32768 bytes/32 KB) for incremental backups. If changing both values, separate them with a space. The block size is equal to (KB size * 2), or (Number of Bytes / 512).

For example, to set the full backup read buffer to 256 KB and the incremental read buffer to 64 KB, enter the following on the first line of the
file: 512 128

You can use the second line of the file to set the tape record write size, also in blocks. The default is the same size as the read buffer. The first entry on the second line sets the full backup write buffer size, the second value sets the incremental backup write buffer size. If we were to set this at the same values, the file would read altogether as:
512 128
512 128

Note: Resizing the read buffer for incremental backups can result in a faster backup in some cases, and a slower backup in others. The result depends on such factors as the location of the data to be read, the size of the data to be read relative to the size of the read buffer, and the read characteristics ofthe storage device and the I/O stack. Experimentation may be necessary to achieve the best setting.

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Pravs's picture

oh, I forgot to tell you that similar stuff already exist in troubleshooting guide for NBU. Please ignore that.  The guide basically mis-guide you :(.  instead of talking in  terms of blocks, it talks in terms of bytes. better leave that until we modify that, til then enjoy this read, bookmart it or trash it ... whatever you wish.

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Shashank's picture

Hi Pravs

    This doc also help me too.

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Anton Panyushkin's picture

I wonder if this mafic touchfile really works for Windows client? Although the pathname for Windows is designated, Windows client seems to ignore this touch file. 

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Pravs's picture

Anton,
I will have a look at this. Thanks for pointing this out. I have updated the article to correctly reflect this.

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Pravs's picture

Hi Anton,

look like it doesn't work or broken somehow.
Ok. I do have other questions for you. I understand that you want to increase your flashbackup performance. is the time to write data to the tape is not so good or it's the time to map the files?

perhaps, you may send me your bpbkar logs for flashbackup with the drive capacity.

Praveen

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Anton Panyushkin's picture

Hello,

We've got a number of Windows file servers that are backed up using FashBackup-Windows policy.
At the moment we are going to move data volumes that are attached to the file servers from HP EVAs to Hitachi NSC disk array, make hardware snapshots of these volumes and attach the snapshots to Windows based SAN media server implementing offhost backup.

 Even though we used FlashBackup policy for this off-host backup, I'm not sure that this approach would give us any benefit. The problem is that we use LAN--based FlashBackup to backup these file servers at the moment and network interfaces on these file servers remain underutilized throughtout FlashBackup.

Could you please give me any guidence on implemention FlashBackup-Windows policies in this case?

 

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Pravs's picture

Interesting, so you are saying that you remain below ~70% utilization on the NIC during a backup?
They should be some plusses from moving to Media server copy in that we will be sending the data right to tape, but you will have the overhead at the beginning of the backup.
I do not think there is enough information here to actually make any decent recommendations.

~ Pravs

Just one person saying to me, “You’ve made my day!” makes my day.

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Anton Panyushkin's picture

The best backup speed I have ever seen is 35-40 Mb/s.
I have tried to lanuch Full backups (or should I say full flashbackups) during workdays when our NetBackup environment is underloaded. Unfortunately, I couldn't gain additional network performance in this case.
Please tell me how I can  deliver bpbkar logs from one or two of our fileservers to you, sowhat you could analyze them.

I'm pretty sure it is not mapping problem, since I observer network underutilization as data is reading from a disk. 

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Pravs's picture

Anton,

please open a support case and our tech-support will be able to help you.
Thanks!

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PrafulPatel's picture

Nice peice of information.

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