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Physical and Logical Reads on different hardware

  • July 4, 2011 at 1:48 am

    #389886

    Hi All,

    I am testing performance of a stored procedure on the same hardware, but two different drives - HDD and SSD. Databases are the same - restored from the same backup and hasn't changed sinse then. I compared the execution plans - they are the same. The SSD one is much quicker, which is what I was expecting, but the strange thing is that number of logical and physical reads is different between two runs - SSD always has less reads. The procedure is called with the same set of parameters, it does exactly the same thing according to the execution plan and returns the same number of records. Does anyone have any idea why they can be different? SSD one always has less reads.

    Thanks.

  • July 4, 2011 at 1:50 am

    #1347651

    SQL Server version is the same:

    Microsoft SQL Server 2008 R2 (RTM) - 10.50.1600.1 (X64) Apr 2 2010 15:48:46 Copyright (c) Microsoft Corporation Developer Edition (64-bit) on Windows NT 6.1 <X64> (Build 7601: Service Pack 1)

  • July 4, 2011 at 5:06 am

    #1347746

    There are a number of possibilities - too many to speculate on. If you would like a precise answer, please post the full output from the two runs with SET STATISTICS IO ON, and actual execution plans (in *.sqlpan format) for the two runs.

    Paul White
    SQLPerformance.com
    SQLkiwi blog
    @SQL_Kiwi

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