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Date: Fri, 10 Dec 2010 17:59:30 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: 1.7.7: upper limit to df reported available size?
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On Dec 10 11:20, Elford,Andrew [Ontario] wrote:
> 11TiB file system displays incorrect available space using df.  'Size'
> and 'used' is correct.  Smaller file systems (6T) are showing correct
> values.
> 
> CYGWIN_NT-6.0-WOW64 server 1.7.7(0.230/5/3) 2010-08-31 09:58 i686 Cygwin
> 
> $ df --version
> df (GNU coreutils) 8.5
> Packaged by Cygwin (8.5-2)
> ...
> 
> $ df -T /cygdrive/f/file
> Filesystem    Type   1K-blocks      Used Available Use% Mounted on
> C:            ntfs    83886076  31717608  52168468  38% /cygdrive/c
> F:            ntfs   11717703676  72036296 -5534201804   -  /cygdrive/f
> L:            ntfs   6143999996 883063196 5260936800  15% /cygdrive/l
> 

Given the surprising simplicity of the statvfs algorithm in Cygwin, I
wonder if this is a bug in df.  Actually, Cygwin just copies over the
lower 32 bit of the Windows value into the POSIX structure.  Assuming a
4K cluster size, this should be ok up to a disk size of about 17 TiB.

Hmm.  OTOH, seeing the size of your FS, I'm also wondering if we should
make the algorithm a bit more foolproof for the future by manipulating
the value of f_frsize if the TotalAllocationUnits returned by Windows
is > sizeof (fsblkcnt_t).


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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