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2820
BB Credit Zero on local ports
Cisco MDS9509 switch, no ISL's, no WAN extenstions, all local within the same datacenter ports. The port utilization is low (for it and others within the same group). I'm getting BB credit zero's counts within WLA on ports that are going to my DMX (1x gets a fairly constant 400-600 for hours, others are spikey with nothing but then get a 2000+ spike). I've heard two differnt things on this, yes it is always an issue because you are holding back an I/O and no it only becomes a big issue on ISL and extended fibre ports.
I'm thinking that it most likely is an issue, but not sure why I'm getting them when I'm pushing less than a 100MB (total send + receive) on a 24 port blade with 4GB connections (so I'm not overloading asic group) and I'm not counting any errors on the port.
healyj
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December 12th, 2017 07:00
Hi there,
In our efforts to clean up the forum, we came across your question / statement.
If the question / statement is still valid, not expired and you need an update please reach out again and we try to get it answered.
As for now we will set it to “answered.”
Regards,
Jim
RRR
2 Intern
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5.7K Posts
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May 14th, 2010 03:00
If the B2B credits are sometimes at 0 that wouldn't be a big problem, since that's what they're there for, but you might want to consider adding a few extra, just to be sure. does anyone agree here ? I've never cmoe accross this locally. The default 16 buffer credits should be sufficient at all times.
AbhishekKS
71 Posts
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July 2nd, 2010 02:00
Hi,
The B2B credits may show that pattern due to several reasons. B2B credit, surge & spikes for example may also depend on the kind of application running through that link. Suppose there is an application which may need to access data in bulk in very short span of time, it may eat the B2B credits fast, on the other side an application which is pretty consistant on its data access behaviour (does not need data in spikes) may not have any affect on the B2B credits. However most of the time the B2B credits shall not show show huge surges or spikes. If this is happening without such a need by the application which is running on the host connected, there may be other reasons for it, like a physical fault in the path such as the cable, SFP at either end or what ever comes in the path like even the HBA or the storage box port etc. You will have to one by one eliminate such possibilities to narrow down to the part of the path which may cause it. However if this is not affecting the performance and things are running fine then all must be ok and should not be a cause of concern.