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sys.dm_io_virtual_file_stats - Number of Read and Writes

  • March 19, 2013 at 10:57 am

    #271794

    I looked up http://msdn.microsoft.com/en-us/library/ms190326.aspx for details on sys.dm_io_virtual_file_stats table.

    and see following descriptions:

    num_of_reads - Number of reads issued on the file.

    num_of_writes -Number of writes made on this file.

    Is it ok to assume that number of reads translate into number of select queries? and

    number of writes translate into number of insert queries?

    thanks

  • March 19, 2013 at 1:19 pm

    #1598615

    No, that's not how those counters work.

    A single SELECT statement can, and very often will, generate multiple physical reads.

    A single UPDATE or DELETE statement can, and very often will, generate multiple physical writes.

    SQL DBA,SQL Server MVP(07, 08, 09) "It's a dog-eat-dog world, and I'm wearing Milk-Bone underwear." "Norm", on "Cheers". Also from "Cheers", from "Carla": "You need to know 3 things about Tortelli men: Tortelli men draw women like flies; Tortelli men treat women like flies; Tortelli men's brains are in their flies".

  • March 19, 2013 at 1:26 pm

    #1598619

    so how can I best interpret this? what does number of read mean? chunks of data in bytes? how big of chunk if that's the case.

    how can I explain number of bytes read in somewhat rather technical detail.

  • March 19, 2013 at 3:19 pm

    #1598651

    sqlstar2011 (3/19/2013)

    so how can I best interpret this? what does number of read mean? chunks of data in bytes? how big of chunk if that's the case.

    how can I explain number of bytes read in somewhat rather technical detail.

    Chances it means the engine read or wrote 64KB of data, the size of an Extent, or 8 pages of data, from or to the file. Just curious, why does this matter to you?

    There are no special teachers of virtue, because virtue is taught by the whole community.
    --Plato

  • March 19, 2013 at 3:35 pm

    #1598654

    Just so I can explain it to the management what a read exactly means and of course for my own self.

  • March 19, 2013 at 4:00 pm

    #1598662

    IMHO the information in sys.dm_io_virtual_file_stats is a bit low-level for management's taste. If you're trying to communicate how busy your server is, maybe for an executive overview or something like that, I would lean towards throwing sdomething like 'transactions/sec' at them.

    There are no special teachers of virtue, because virtue is taught by the whole community.
    --Plato

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