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How to make a file of an size fast - fsutil file createnew test 1048576

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https://stackoverflow.com/questions/982659/quickly-create-large-file-on-a-windows-system

http://technet.microsoft.com/en-us/sysinternals/bb897428.aspx


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Modified 10 months ago
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In the same vein as Quickly create a large file on a Linux system, I'd like to quickly create a large file on a Windows system. By large I'm thinking 5 GB. The content doesn't matter. A built-in command or short batch file would be preferable, but I'll accept an application if there are no other easy ways.

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24 Answers

487
fsutil file createnew <filename> <length>

where <length> is in bytes.

For example, to create a 1MB (Windows MB or MiB) file named 'test', this code can be used.

fsutil file createnew test 1048576

fsutil requires administrative privileges though.

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  • 6
    @ZXX +1 For my purposes I merely needed the file system to see the space as unavailable, but your information is helpful if someone else needs this. 
    – Leigh Riffel
     Dec 22, 2010 at 13:50
  • 24
    fsutil file createnew does not create a sparse file. 
    – Per Mildner
     Jun 30, 2013 at 17:58
  • 10
    "fsutil sparse setflag temp.txt" sets the sparse flag, making it a sparse file. "fsutil sparse setrange temp.txt 0 1024" sets the range of sparseness :) 
    – Coldblackice
     May 10, 2014 at 21:53
  • 3
    @ZXX fsutil file createnew does NOT create sparse files: c:\>fsutil file createnew test.txt 0x100000 File c:\test.txt is created c:\>fsutil sparse queryflag test.txt This file is NOT set as sparse 
    – ivan_pozdeev
     Oct 20, 2017 at 6:29 
  • 4
    This might not technically be a sparse file, but creating a 500GB file takes less than a second (even on a somewhat faulty hard disk). If you want to actually trigger 500GB of disk IO (like I do), this command isn't it. 
    – Simon Kissane
     Oct 5, 2018 at 7:43 
39

You can use the Sysinternals Contig tool. It has a -n switch which creates a new file of a given size. Unlike fsutil, it doesn't require administrative privileges.

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