I have a system that is showing high response times and latency at the LUN level but the array is under utilised on everything else (pool, cache, controller, ports etc).
I think the issue is likely with the network but if that is the case wouldn't there be something indicative at the cache or controller level as well as the LUN?
Thanks in advance.
First - what type of connection are you talking about? Fibre channel or iSCSI?
Second - where are you measuring the LUN Response times - on the array or on the host?
Third - on VNX when the IOPS are very low (typically under about 120 IOPS) the Response Times can be very high - this is do to the use of Little's Law to calculate the Response Times. See https://support.emc.com/kb/453230
Fourth - it is possible that problems at the SAN level like bad / not clean optical cables or switch problems cannot be seen in the VNX stats affect performance