Port congestion index and high zero buffer credit figures

[kevsta]

Hi Guys,

I have two IBM SAN96b's connected via 8GB E port ISL's the distance between them is less that 2K/3 miles.

I seeing high numbers in the port congestion index and high zero credit buffers figures.

portperfshow shows that im only sending about 10mb on average down the ISL, is it possible that im sending too many frames at the E port?

If so whats the best way to reduce this?

It doesnt seem to be a bandwidth issue more like the switch cant deal with the amounft of frames, is this thinking correct?

Thanks

[Antonio Bongiorno T…]

@kevsta

can you post please a bit more info ?

is a point-to-point fibre ?

WDM ? if yes Vendor / Model ?

what type os SFP are you using ?

how is the port settings ?

is QoS enable or disable ? in most case this is the first cause by long distance.

[Thierry.Zimmermann]

Hello,

Are you seeing timeouts or discards on any port?

What application are you running (SVC, VTS, others)?

[Thomas.Letsche]

Hi kevsta,

the buffer credit zero counter is just an indicator influenced by many different factors, e.g. link distance, allocated buffers, average frame payload size, enabled features, possible backpressure, etc...

The question always is, what is considered high...

Can you please share the output of portstats64show of the ISLs with us?

TL