Slow ISL

 
Eric Delaet
Occasional Advisor

Slow ISL

Hello,

I have 2 Eva4400's. 2 Servers (1&2) are connected on the internal switch of Eva1, another server (3) is connected on the internal Switch of Eva2. It has the same LUNs as the other servers mapped on Eva1 (so Eva2 is not mapped, just it is used as DR). There is an ISL between the 2 switches. The internal switches of the Eva are 8 GBit.

I've noticed speed differences between Server3 and the other 2 servers. It seems that the ISL slows down my throughput.

I.e. I have one stream which takes 4.30 minutes to finish on server 1 & 2, and 5 minutes on server 3.

Is this speed difference normal if I map a server on another SAN via an ISL ?

Thanks.
2 REPLIES 2
Mario_66
Valued Contributor

Re: Slow ISL

It can happen. Have you checked buffer to buffer credits? DR is going over the same ISL?

BR,
Mario.
Eric Delaet
Occasional Advisor

Re: Slow ISL

Hello,

Thanks. Yes, true, the DR is going over the same ISL. But the ISL is 8 GBit, it's almost impossible to saturate it with the throughput we have. I'm sure it is not saturated, but is there a way to check/monitor this?

As far as I know, buffer credits only occur when there is an intermediate link with another speed in between. This is surely not the case with us.

Do I understand it correctly that, if the link is not saturated and there are no buffer credits, the ISL shouln't affect the speed?