I was trying to use DiskSpd to check IO subsystem performance but one thing I was confused about is regarding the -T switch, which (according to the documentation) is the number of threads per file. As I understand it, this is the number of cores I have, for example, if I have a 6-core server then this is the maximum -T value I can use.

Please advise if I am missing something here. Normally the parameter looks like below:

diskspd.exe -b2M -d60 -o32 -h -L -t56 -W -w0 O:\temp\test.dat > output.txt

Reference: Getting Started with Diskspd (Brent Ozar)

  • 2
    The appropriate value for threads depends on type of SQL Server IO you are simulating, which may exceed the number of available cores and should be based on MAXDOP. The example looks to be focused on read-ahead reads due to the 2MB IO size. Note the threads parameter is lower-case t (upper case T is the offset). Threads can exceed the number of cores. – Dan Guzman Oct 21 '18 at 12:30

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