Will this kind of operation cause a lot of split I/O?

JasonYangJW 61 Reputation points

Our applications are running on Windows Server 2012, and we found that a lot of split I/O produced.
We use Process Monitor to monitor the events of our applications,and found that they are writing log file with bellow behavior.

Split I/O(Windows performance counter):

  1. CreateFile


w3wp.exe 14332 CreateFile D:\CTOSP\TOSlogs\DIS\log.perf.2021-02-20 SUCCESS Desired Access: Generic Write, Read Attributes, Disposition: OverwriteIf, Options: Synchronous IO Non-Alert, Non-Directory File, Open No Recall, Attributes: n/a, ShareMode: Read, AllocationSize: 0, OpenResult: Created

  1. QueryFileInternalInformationFile


w3wp.exe 14332 QueryFileInternalInformationFile D:\CTOSP\TOSlogs\DIS\log.perf.2021-02-20 SUCCESS IndexNumber: 0x10000000371c1

  1. WriteFile(Do small size WriteFile calls like bellow for multiple times until the file reach 5MB)


w3wp.exe 14332 WriteFile D:\CTOSP\TOSlogs\DIS\log.perf.2021-02-20 SUCCESS Offset: 0, Length: 530, Priority: Normal

  1. QueryAttributeTagFile


w3wp.exe 14332 QueryAttributeTagFile D:\CTOSP\TOSlogs\DIS\log.perf.2021-02-20 SUCCESS Attributes: A, ReparseTag: 0x0

  1. QueryStandardInformationFile


w3wp.exe 14332 QueryStandardInformationFile D:\CTOSP\TOSlogs\DIS\log.perf.2021-02-20 SUCCESS AllocationSize: 51,249,152, EndOfFile: 51,219,242, NumberOfLinks: 1, DeletePending: False, Directory: False

  1. CloseFile


w3wp.exe 14332 CloseFile D:\CTOSP\TOSlogs\DIS\log.perf.2021-02-20 SUCCESS

I am wondering if this kind of operations caused many split I/O?
As I know split I/O means that large I/O request seperated to small ones.
But as above operations shows, the applications are doing very small size WriteFile calls.(check the WriteFile length)
Or maybe it is not caused by this kind of operations, which means we have to check if there is any other reason?

Windows Server 2012
Windows Server 2012
A Microsoft server operating system that supports enterprise-level management, data storage, applications, and communications.
1,556 questions
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Accepted answer
  1. AliceYang-MSFT 2,081 Reputation points


    It is not effective for us to do log analysis here in the forum. Therefore, I would like to suggest that you contact Microsoft Customer Service and Support (CSS) via telephone so that a dedicated Support Professional can assist with your request.

    Here are two ways
    Microsoft Support for business
    Global Customer Service phone numbers

    Log file logs what happened. Split I/O might occur if the program requests data in a size that is too large to fit into a single request or if the disk is fragmented. Factors that influence the size of an I/O request can include application design, the file system, or drivers. So I think the answer is yes. Please see, Split IO meaning.

    Please note: Information posted in the given link is hosted by a third party. Microsoft does not guarantee the accuracy and effectiveness of information.


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