Pause Output Errors

Unanswered Question

Hello, I have an interface on a 6509 connected to a server that is reporting Pause Output Errors.  This is the first time I have seen this type of error and I was hoping to find some suggestions on how to troubleshoot the problem.  We have several hundred devices connected to two 6509 switches in our data centre but this one server appears to be the only one experiencing the issue.

Thanks

Jamie

I have this problem too.
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Jon Marshall Mon, 04/26/2010 - 05:18

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Hello, I have an interface on a 6509 connected to a server that is reporting Pause Output Errors.  This is the first time I have seen this type of error and I was hoping to find some suggestions on how to troubleshoot the problem.  We have several hundred devices connected to two 6509 switches in our data centre but this one server appears to be the only one experiencing the issue.

Thanks

Jamie

Jamie

Pause outputs occur when the receiving port is getting overloaded and the so the switch sends a pause request to the device connected to the port. Most modules on the 6500 do not support full wire rate on all ports so it could just be that you have oversubscription.

Are you noticing any performance issues with the server ?

Jon

Giuseppe Larosa Mon, 04/26/2010 - 06:10

Hello Jamie,

that is simply a counter of IEEE pause frames sent to neighbor.

Each PAUSE frame asks for a little silence time interval to the other device.

(the time equivalent of 512 bit times)

see

http://en.wikipedia.org/wiki/Ethernet_flow_control

Instead of having input errors of type ignored or overrun you see PAUSE frames sent out.it is a tradeoff.

PAUSE frames are used to implement flow control they are not bad by themselves.

I see you have also output drops:

>>> Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 47747

>>>> 0 lost carrier, 0 no carrier, 887994 PAUSE output

as Jon has noted this can be the sign of an oversubscribed LAN linecard.

What type of linecard is the port part of?

only C6748 has very high performance, lower series have high oversubscription ratio.

Edit:

clearly the server can have output drops as a result of the silence intervals asked by switch port.

Hope to help

Giuseppe

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