Hello,

I'm seeing performance information from Analyzer on the SPA of my VNX 5500 (with FAST Cache) that I have some trouble to clearly understand.

Actually the ABQL (Average Busy Queue Length) is continuously around 32, but if I check the QL (Queue Length) it is around 3 and the RT (Response Time) is around 2 ms.

Now from the Book ->

ABQL:

Desc: Average number of requests waiting at a busy system component to be serviced, including the request that is currently in service.

Comment: Since this queue length is counted only when the SP is not idle, the value indicates the frequency variation (burst frequency) of incoming requests. The higher the value, the bigger the burst and the longer the average response time at this component. In contrast to this metric, the average queue length does also include idle periods when no requests are pending. If you have 50% of the time just one outstanding request, and the other 50% the SP is idle, the average busy queue length will be 1. The average queue length however, will be ½.

QL:

Desc: The average number of requests within a certain time interval waiting to be served by the component, including the one in service.

Comment: A queue length of zero (which is average) indicates an idle system. If three requests arrive at an idle SP at the same time, only one of them can be served immediately; the other two must wait in the queue, resulting in a queue length of three.

How can I have an ABQL of 32 when I'm only having a QL of 3 especially if the RT is at 2 ms?

Thank you in advance for your help

Eric