Last week I was traveling to and from our Austin office – which means a fair amount of time for reading. Amongst other books, I read “The Principles of Product Development Flow”, Reinertsen, Donald G. The most interesting part of this book (to me) was the chapters on queueing theory.
Little’s law shows the Wait time for a process = queue size/processing rate. That’s a nice intuitive formula, but with broad applicability.
So what does this have to do with monitoring? (more…)
If you have decent NetApp monitoring, you should of course be monitoring the thing that matters – and (for most applications) that is the latency of requests on a volume (or LUN.)
Easy enough to get – with LogicMonitor it’s graphed and alerted on automatically, for every volume. But of course when there is an issue, the focus changes to why there is latency. Usually it’s a limitation of the disks in the aggregate being IO bound. Assuming there is no need for a reallocate (the disks are evenly loaded – I’ll write a separate article about how to determine that), how can you tell when what level of disk busy-ness is acceptable? Visualizing that performance like the below is what this post is about.
