I/O I/O - off to work I go..

Last Post 09 Jun 2009 07:18 AM by SQL_Jr. 2 Replies.
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SQL_Jr
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03 Jun 2009 06:57 AM
I have a question about I/O statistics. I am using the SQL2k5 dmv that returns me stats (in percentage) by database, and by drives. I am trying to understand the results, and figure out when it should be a concern.

For example, if I see one particular database/file is returning >90% of I/O on a particular drive, does this indicate a potential problem of contention?

Also, what is the best way to measure - a percentage out of one single drive, or overall percentage out of all cumulative drives? I think if a particular db is showing 90% on one drive, that is a better way to look at it, b/c IO is bound to a drive? Does this make sense. Please comment!
SQL_Jr
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04 Jun 2009 07:36 AM
hi, gunneyk:

Yes, I am using sys.dm_io_virtual_file_stats, and joining it with sys.master_files, and derive a percentage for each row out of the whole.'
So, based on the above, what do you think a useful "threshold" would be?
Let me know! Thx

SQL_Jr
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09 Jun 2009 07:18 AM
HI, gunneyk.

Thanks for info. I was wondering, sometimes I see a sql server error
SQL Server has encountered 1 occurrence(s) of I/O requests taking longer than 15 seconds to complete on file X....
Does this relate to the IO Stall MS? Explain how I can capture that, or how sql server gets that error.

THX


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