Resource monitor and how to spot if you have disk I/O problems?

Question

I have an application server which runs pervasive SQL and app using it. Last weeks the users are complaining about poor performace of the app and I suspect disk I/O problems because CPU and RAM usages are just fine.

Here are my resource monitor graphs and if you could please tell me how to properlly read them and if I have problems with disk I/O.

• Disk C: - system disk
• Disk E: - application with all its data

Solution

Disk queue length is usually the first place to look at. If it is just SQL on the disk (assuming it partitioned correctly) then a queue over 1+ is problem time unless you are doing massive disk based queries.

In the resource monitor that you have open, you can also expand down the section on the left and order by queue to see which application is hogging the disk.

If it is only SQL that is slow, perhaps you might be better looking at any slow queries on the server throughout the time period. SQL is also CPU bound in most applications I've worked with.