Fiber backup slower than LAN, why??

[dglee]

I've got a new media server here that is connected directly to our tape library (adic i500) via fiber.  we were having issues with detecting the library from the media server, so while we were troubleshooting, i was backing the server up over the LAN, as if it were just a client.  For the time that we were backing it up this way, I was getting a throughput of about 35MB/s.

now that we've gotten our installation issues resolved, I changed the backups so that they run the way we had intended, directly via fiber.  However, with the jobs running over the fiber, we are only getting throughput of about 10MB/s.  I'm backing up the exact same data, yet the data rate is running at a third of the LAN.  Can someone give me an idea about why this is happening?

also, why is my username a random number, and where can i change that?  i can't seem to do it from my profile page.

Message Edited by 289703687 on 04-17-200712:07 PM

[dglee]

bump.

[Tim_Chapman]

start by checking the bptm log on the media server and look for 'waited for full buffer nn times' or 'waited for empty buffer nn times'. This will tell you whether its because you are unable to get the data to the tape quick enough or whether its because you are getting too much to it. You can then modify your buffer sizes accordingly.

If you are attaching via a SAN switch check the SAN switch performance during a backup to see how much data is passing over the port. Finally, check the firmware/bios of the FC hba and its settings to ensure that it is not the bottleneck.

hth

[Rakesh_Khandelw]

Check your Buffer and Block size settings for NBU and OS.

- Backup Planning and Performance Tuning Guide for UNIX, Windows, and Linux (  http://support.veritas.com/docs/281842 )

[dglee]

Thanks to the both of you...I'm going to do some follow up research and try out your suggestions.

[dglee]

Rakesh,
In the support article, it instructs me to do this:

To troubleshoot performance issues related to buffer settings, enable and review the bptm log on the media server and the bpbkar log on the client.

This machine is the media server and I'm trying to back up data on itself.  Do I look through both?  Also, how do I change my user handle so that it isn't just a random number???  I can't find a place to do it in my profile.  Thanks again.

darren

[Liew_WK]

Hi,
If you are sure same client and data, so you may check this from both of your media server

1. media server platform ? Is it same ? Windows media server giving slower performance
2. http://seer.entsupport.symantec.com/docs/183702.htm

NET_BUFFER_SZ
SIZE_DATA_BUFFERS
NUMBER_DATA_BUFFERS

I just prove this tuning give 5x (backup eprformance) different from same client & data backup.

Liewwk