title: Estimating IOPS requirements of a production SQL Server system
body: <p>We're working on an application that's going to serve thousands of users daily (90% of them will be active during the working hours, using the system constantly during their workday). The main purpose of the system is to query multiple databases and combine the information from the databases into a single response to the user. Depending on the user input, our query load could be around 500 queries per second for a system with 1000 users. 80% of those queries are read queries. </p>
  
  <p>Now, I did some profiling using the SQL Server Profiler tool and I get on average ~300 logical reads for the read queries (I did not bother with the write queries yet). That would amount to 150k logical reads per second for 1k users. Full production system is expected to have ~10k users. </p>
  
  <p>How do I estimate actual read requirement on the storage for those databases? I am pretty sure that actual physical reads will amount to much less than that, but how do I estimate that? Of course, I can't do an actual run in the production environment as the production environment is not there yet, and I need to tell the hardware guys how much IOPS we're going to need for the system so that they know what to buy.</p>
  
  <p>I tried the HP sizing tool suggested in the previous answers, but it only suggests HP products, without actual performance estimates. Any insight is appreciated.</p>
  
  <p>EDIT: Main read-only dataset (where most of the queries will go) is a couple of gigs (order of magnitude 4gigs) on the disk. This will probably significantly affect the logical vs physical reads. Any insight how to get this ratio?</p>