I want to test my different SQL Server alternatives with a benchmark tool. I found two tools by Microsoft:

  1. SQLIO Disk Subsystem Benchmark Tool
  2. SQL IO Sim

What are the differences between them? is it the same thing?


2 Answers 2


SQLIO is a generic tool for testing your disk subsystem. It allows you to specify whether to test random/sequential, data block sizes, queue depth, threading, etc.

SQLIOSim is a tool that tries to emulate the patterns that SQL Server would expose to your system.

Usually I'll use SQLIO to test the subsystem when benchmarking for raw specs. Once satisfied with my SQLIO results I'll run SQLIOSim to get a real world run through of the disk subsystem.

You might want to see Brent Ozars tutorial on SQLIO, which also mentions SQLIOSim: http://www.brentozar.com/archive/2008/09/finding-your-san-bottlenecks-with-sqlio/


Note: I came here from another answer where I misstook SQLIO for SQLIOSim. Hopefully I'll get it right this time. :-)

SQLIOSim is "NOT" an I/O Performance Tuning Tool because it uses random patterns, so is not repeatable (a primary requirement for benchmarking). It is a stress-testing tool.

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