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Re: HFS + and creating a big file
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Re: HFS + and creating a big file


  • Subject: Re: HFS + and creating a big file
  • From: John Francini <email@hidden>
  • Date: Sat, 10 Jun 2006 15:37:23 -0400

Title: Re: HFS + and creating a big file
HFS+ does not support sparse files.  Therefore, the OS must do what you observed: allocate the space and fill the file up with zeroes at file close or flush.  Period.

Therefore, you have two choices:

1. Use a different type of file system, like UFS, for this particular file and application.

2. Live with it.

3. Use a sparse disk image file (which can be created with Disk Utility/hdiutil), which will effectively do what you're looking for, although with some amount of overhead because of the "wheels within wheels" aspect of disk image files.


Best regards,

John Francini

At 12:31 -0400 6/10/06, Marc Van Olmen wrote:
hi,

I need to create a big file (20GB), the contents is not important, will fill that in later, just the file size...
When I try to do this with lseek and then write one byte. as soon I close the file, it takes a few minutes because it looks like the OS is filling up the rest with 0x00 bytes during close or flush. File system is HFS+

Any trick on how to prevent this from happening?

regars,

marc
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References: 
 >HFS + and creating a big file (From: Marc Van Olmen <email@hidden>)

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