I see disappointing performance on our Netbackup master where clients are transferring data at a rate of between 5-6MB/sec where all the equipment supports gigabit speeds.
We have a secondary Netbackup master that sees speeds of 25MB/sec or so from the same clients.
Running TTCP tests yields 7-8MB/sec with the slow master as the receiver and between 50-100MB/sec on the secondary.
TTCP tests also yield 7-8MB/sec to other servers on the same switch as the slow master, and all this slow behavior is intermittent. About half the time, things run much faster.
Wireshark captures on the slow receiver show dupacks being sent, and captures on the sender show psh/acks being sent. The sender is not sending duplicate packets, and the switches report no dropped packets. In addition, the receiver periodically sends Zero Window packets.
I see a communication delay between the receiver and sender, but the sender sends acks right after it receives packets, and the sender sends packets right after getting acks. And yet both sides seem to be timing out. That is my amateur nterpretation, but our network admins say that ping and traceroute tests show no delays.
I am very skeptical, but I don't know anything about Cisco devices to ask them what to look for.
They say their switches are pretty plain vanilla, using mostly default settings. They won't send me a copy of the switch config, so I don't know what this means.
In the searches I have done, I suspect some kind of flow control or congestion avoidance is going on.
Cisco documents provide a lot of information regarding what to look for in terms of logs, counters and configs, but I am not being given this information.
So, does this behavior ring any bells?
And where can I find what the default configuration of a Catalyst 3750 are?
Thanks for any help.