If you suspect that your SQL Server instance is having Disk I/O issues, these queries can help furnish proof that you are under I/O pressure, and they can help pinpoint what is causing the problem.
Before you run determine that you have I/O issues, please verify that by running Top Wait Stats rollup query.
-- Always look at Avg Disk Sec/Read and Avg Disk Sec/Write in PerfMon for each Physical Disk
-- Check for IO Bottlenecks (run multiple times, look for values above zero)
SELECT cpu_id, pending_disk_io_count
WHERE [status] = 'VISIBLE ONLINE';
-- Look at average for all schedulers (run multiple times, look for values above zero)
SELECT … Read the rest