2 – Each bucket represents a range of queue depths seen when an item is added to the
queue.
3 – Two counters are maintained for each bucket
queue depth count – Number of events when the queue is within this bucket’s range
accumulated queue depth – The Sum of the Queue Depths when an event enters this
bucket
So, when an IO enters the queue (comes from a host to the director) the first thing
checked is the depth of the queue at that moment. Two things happen:
A – The appropriate accumulated queue depth bucket is incremented by the queue depth
value observed.
B – The queue depth count is incremented by 1 (one more IO for this bucket)
For each of the buckets an average queue depth is calculated by dividing the
accumulated queue depth by queue depth count.

Hi InsaneGeek,

I think the following gives an answer to your question:

The two sets are the “accumulated queue depth” and the “queue depth count”.    On the IO’s arrival, the queue depth is established and this (the number of IOs ahead of this one in the queue) is added to the appropriate accumulated queue depth bucket.    The equivalent bucket in the queue depth count set is incremented by one. From these two sets a third set of equivalent buckets is derived: the "average queue depth" is the "accumulated queue depth" divided by "queue depth count".

Regards,

Kl.

That's what I was looking for thanks!