Monitoring disk usage in Windows with RAM caching

Question

I'm monitoring disk activity on my machine using Windows Performance Monitor (perfmon). I'm interested in the Collector sets LogicalDisk > % Disk Time and LogicalDisk > Current Disk Queue Length. I ran some heavy applications, and I noticed that during the first load time, these numbers shot up, as expected. However, I wasn't able to replicate the results. This is because Windows caches files on unused RAM. So, when I was trying to monitor the disk usage the second time, Windows had cached everything, and it showed no disk activity.

My question is this: is there a way to monitor these "virtual" IO requests? I don't want to turn the smart caching off, as it greatly increases load time, I'd just like to continue to grab IO information, regardless of where Windows is storing the information. (On RAM or on disk.)

Answer 1

You can monitor quite a bit about the cache from performance monitor.

Simply add what you are interested in with the green "+" at the top, select "Local Computer" and then drill down to what you want under the "Cache" options.

(Understandably) windows manages memory from the cache differently than from the hdd, so the options won't be measured in quite the same way as reads from the hard drive. Check out this msdn article for what the options there actually mean.