Profiling disk access

Question

Currently I am working on a MFC application which reads and writes in to the disk. Sometimes this application runs amazingly fast and sometimes it is damn slow. I am guessin

Answer 1

You can use the Windows Performance Toolkit for this. You can enable trace providers for disk I/O events and see the I/O time and disk service time for each. It does have a bit of a learning curve though. This will also let you determine which file I/O's actually result in real-access to the disk and aren't handled by the cache manager.

Most important parameters are disk service time and queue length. Disk service time is how long the disk actually took to service the request. Queue length indicates if your disk request is backed up behind other requests.

For many threads w/ reads & writes - Many disks have poor performance in the face of reads with background writes. If you have various threads doing lots of disk I/O to random locations on the disk, you may wind up starving certain requests.