Using autoMax4G and TE ports

[dynamoxxx]

Hello guys,

i have a 9513 with 8G capable 24 port card. I will be connecting a 9124e switch that is a 4G capable switch. The 9513 will have NPIV enabled and 9124e will be converted to NPV mode. Typically when i connect two identical speed switches together (TE mode) i set ports on each side to "dedicated" RateMode. In this case i don't want to dedicate 8G on 9513 for connection that is going to a 4G switch. So i was thinking of using autoMax4G on 9513 side, does anybody see any problems with doing that ? Since 9124e it's going to be in  NPV mode, it will login as F port and not TE port.

Thank you

[blueyonderguy]

since you are connecting NPV switch, it would create a NPV link and not an ISL. it would login as a host (F port) so AutoMax4G would limit the uplink to 4Gig. You would be good by setting it to auto as the link would negotiate to 4gig anyway.

keeping both in dedicated mode might not be able to bring up the link.

[dynamoxxx]

what if i simply set the speed to 4G and rateMode "dedicated" ? I can't think of any issues with that ..can you ?

[blueyonderguy]

dedicated rate mode assigns all BB credits to that port. It can be wasteful if your NPV link is not being pushed aggressively. keeping it in F-dedicated would assign less credits to begin with and then provide more as utilisation increases (and if other ports are not blocking those).

generally you would have multiple NPV uplinks so blocking BB credits for all would not be straightforward call. depending on utilisation profile of other ports, you can decide.

[dynamoxxx]

dedicated rate mode assigns all BB credits to that port. It can be wasteful if your NPV link is not being pushed aggressively. keeping it in F-dedicated would assign less credits to begin with and then provide more as utilisation increases (and if other ports are not blocking those).

i will have one NPV link per 9124e. I am not sure what you mean by "F-dedicated".  Since 9124e is 4G capable, on my 9513 8G capable switch i was going to set port RateMode: dedicated and speed 4G.  I would think setting dedicated for an NPV uplink makes sense ?

[blueyonderguy]

Point i was trying to make is that whenever you set dedicated speed on any port, you reduce BB credits from the global pool. this is wasteful if the port is not going to be driven to maximum performance by the connected host (NPV link in your case)

about setting up 4G speed between 4G and 8G port, I do not see any issues.

[dynamoxxx]

i see your point, my concern is that by not setting the NPV port to dedicated, an 8G connected host (actually driving that much throughput) could starve my NPV link and affect all the hosts behind it (blade servers).