[Veritas-bu] ESL Poor LAN Performance

2013-11-19 14:12:11
Subject: [Veritas-bu] ESL Poor LAN Performance
From: mstoller <nbu-forum AT backupcentral DOT com>
Date: Tue, 19 Nov 2013 11:12:06 -0800
With a 10x performance difference between backing up to the LTO4 drives and the 
LTO5 drives, I'd suggest checking the fibre path from the server to the tape 
drive in the LTO4 library and comparing it to the LTO5 library.  You might want 
to check port errors at the switch.
I have my doubts this is an issue of the data going too slow and bogging down 
the LTO5 - I typically don't see such a large performance hit in those cases.

- is anything elses backing up to the LTO5 library? 
- if so, is the performance similar to this job?
- have you try a different job from this server to the LTO5 and 5 libraries and 
seen similar performance discrepancies?
- have the drives in the LTO5 library been updated to current firmware levels?

I don't have definite answer on this one, but here are a few recent issues I've 
seen that led to poor backup performance when going to different drives (maybe 
they'll help point you in the right direction?):

1 - I doubt this is the case at your site, but I have seen an instance where 
traffic from one media server was routed through a different server before 
going to the tape drives - so, the data went from client A to media server 1 
over the LAN , then out the LAN to media server 2 and then across the SAN to 
the drives - in this case the LAN was the bottleneck. I believe this was a case 
of picking the wrong storage unit for a job.  It's worth taking a look at.
2 - Another thing to look at: I recently ran into a case at a customer site 
with slow performance to the drives on one library vs. going to a different 
library.  It turns out that the fast library's drives were plugged directly 
into the switch that the servers were also plugged into, while the slow 
library's drives were plugged into a switch that was connected to the first 
switch with a 1Gb/s link - and there were many devices attached to that second 
switch, all trying to get data through that 1Gb/s link.  Just too much 
competition for limited bandwidth.


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