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Need help with tuning NetBackup data buffers (slow duplication jobs to tape)

swatts7605
Level 0

Hi,

I'm relatively new to NetBackup, but we're seeing slow performance, mostly with duplication jobs to our LTO5 tape library.

Here's a summary of our setup:

NetBackup v.7.6.0.3

Appliance:  5220

StorageTek SL150 tape libary (4 LTO5 tape drives)

SLPs:  Write to PureDisk (34TB disk shelf) w/ retention of 5 weeks with a duplication job to tape (w/ 1 year retention)

LTO5 settings:  Max concurrent drives = 2; Multiplexing Max Streams per drive = 6; Fragment size = 5000MB

PureDisk settings:  Max concurrent jobs = 25; Max fragment size = 5000MB; Max I/O streams = 75/volume

Master (the only media server):  Max jobs per client = 30; Min size per duplication job = 80GB; Max size per duplication job = 120GB

We've modifed the SIZE_DATA_BUFFERS for both tape and disk to 262144 and NUMBER_DATA_BUFFERS to 256.  We've also decreased our max concurrent tapes drives from 4 to 2, which seems to have helped a bit.

On our duplication jobs, we're only seeing around 15-20mb/sec throughput, while catalog backups are running around 80mb-100mb.  Our HPUX/Unix clients are backing up around 60-80mb/sec, but our Windows clients are the ones that are suffering.

Log files are showing that there's too much time being wasted on tape positioning, waiting on full buffers and delays in filling those buffers.

It doesn't appear that we can push enough data to the tape drives and they have to constantly wait for more data before writing it to tape.

Example output from a recent job:

10/21/2015 16:33:07 - Info bptm (pid=21989) waited for full buffer 49882 times, delayed 145940 times
10/21/2015 16:33:11 - end reading; read time: 0:05:45
10/21/2015 16:33:11 - Info bptm (pid=21989) setting receive network buffer to 1048576 bytes
10/21/2015 16:33:12 - Info bpdm (pid=22016) completed reading backup image
10/21/2015 16:33:16 - Info bpdm (pid=22016) using 256 data buffers

Are there any settings that we're overlooking that would speed up performance, mainly on the duplication jobs to tape?

1 ACCEPTED SOLUTION

Accepted Solutions

Marianne
Moderator
Moderator
Partner    VIP    Accredited Certified

.... waited for full buffer 49882 times, delayed 145940 times

 

I don't think any kind of buffer tuning will help here - it seems that read speed from disk is very slow.

Have you included the 4TB head unit in your de-dupe volume? If so , it will slow down the de-dupe performance.

Please also have a look at this post :

 Slow Duplication and Replication Issue 
and this one:
NBU 5220 Performance 

View solution in original post

3 REPLIES 3

WVT
Level 4
Partner Accredited Certified
https://www.veritas.com/support/en_US/article.TECH75213 try this to prove things out. It will use up space so keep retention to days and create seperate policy, volume pool, etc. Dupe from disk to tape does not use multiplexing. if you have questions, ask.

RiaanBadenhorst
Moderator
Moderator
Partner    VIP    Accredited Certified

Hi,

 

Your first and most important action is to upgrade to a version higher than 7.6.1. There are major changes and improvements relating to rehydration (duplicate from dedupe to non-dedupe) in this version.

 

Once you've done that you can look at fine tuning with buffers / touch files etc.

Marianne
Moderator
Moderator
Partner    VIP    Accredited Certified

.... waited for full buffer 49882 times, delayed 145940 times

 

I don't think any kind of buffer tuning will help here - it seems that read speed from disk is very slow.

Have you included the 4TB head unit in your de-dupe volume? If so , it will slow down the de-dupe performance.

Please also have a look at this post :

 Slow Duplication and Replication Issue 
and this one:
NBU 5220 Performance