io_stall question

I just installed SQL Server on new hardware and ran a test script to show io_stall information by file. Nothing else has been loaded yet, just a fresh install of SQL Server 2012. Why are the io_stalls for reads and writes high? See output below. We are using separate SSD drives for data, logs, etc.

I really don't think you have anything to worry about here. Unless you mean a completely separate SSD + controller for every individual file, there are always going to be competes for concurrent read/write activity. Even then I suspect the OS can't write to 20 different files at the same time without any of them waiting on each other to some minor degree.

As a reference, I ran the same script you did on my lowly local VM, which has a single disk, and here is what I see (click to enlarge):

Worry about it when I/O is actually a symptomatic problem based on other observations as well, not just because your io_stall number is non-zero.

StackExchange Database Administrators Q#89951, answer score: 2