Maximum Traffic Utilisation on fc Links

[steve switzer]

Hi

We are looking at re-configuring our SAN and the question came up as to whether

the Interswitch link could handle the additional throughput.

My fellow engineer was convinced that the fibre channel links (being fibre) could approach

100% without failing). However i am convinced this is not the case.

So even though our links are nowhere near that much utilised does anyone know what the

maximum % throughput would be on a given link or channel group.

We are nowhere near this but it would help to know what the official numbers are for this

Steve

[kenk]

Hi Steve,

MDS ISL links can certainly achieve full utilization.

However, customers concerned about maintaining connectivity to storage generally plan for the

unexpected ISL link failure (e.g. A port channel with two member links should be utilized less than 50% at peak so that

a failure of one link allows the other to take over all the traffic load).

Fibre Channel uses a buffer credit scheme to provide back pressure to upstream devices during congestion on a link

by link basis.  So, if your Port Channel is running at 100%, you should expect buffer credit starvation at the end devices.

Regards,

Ken