Very simple. It is what it says:
SQL Server has encountered 3 occurrence(s) of I/O requests taking longer than 15 seconds
SQL Server makes a IO request, it takes more than 10 seconds to complete. Normally it should take - for a high performance database server - 2-3 ms, not 15.000 or more.
The file path:
[C:\Program Files\Microsoft SQL
Makes me suggest you dont have a production server but someone who had no clue how to install a sql server orderd the hardware and set it up. As a result your database files live on the (slow?) system drive instead of having an IO optimized setup, and your disc simply is totally overlaoded. Happens when one runs high performance databases on a system disc instead of an optimized disc layout. Database servers are tricky to configure hardware wise.
Only solutions are:
- Check for missing indices. Table scans - especially wehen memroy is not enough - are very IO itensive and can overload every IO subsystem.
- If query optimization does not yield results, then get a proper deatabase server with a number of faster discs. At the end, your productzion database may jsut need more IOPS than the slow system drive provides.
Just as exmaple, I have a smaller database here (800gb) and I use 8 Velociraptors as a RAID 10 for the databae file and 2x120gb SSD for the logs - which nicely separates out the log IO from the database IO. And I am not happy with the database file disc IO and will soon upgrade with SSD caches.
NOTHING (except the very low usage system databases) exists on C.
The fact that you dont mention your disc layout on a IO related question makes me suggest you dont know how databases work IO wise and someone just ordered a cheap dell server thinking that "it has a xeon, so it is fast" while databases often dont care about the CPU and are totally IO bound.