Re: du -m is off

[David Laight <david%l8s.co.uk@localhost>]

On Sat, Mar 22, 2008 at 01:10:04PM -0400, Greg A. Woods; Planix, Inc. wrote:
> 
> Now as to the problem with your 10485760-byte file, well that's easy  
> to understand if you first take a peek at just how much space has  
> been allocated for that file (and keep in mind that "du" shows disk  
> usage, not file size) [use "stat -s"].  For example when I create an  
> exactly 10MB file I get a file that uses 20512 "blocks" (i.e. 512- 
> byte-blocks) of disk space.  If you multiply that back out then the  
> bytes of disk space used are 10502144, i.e. 10.015625MB, and so by  
> the logic above that means that in 1MB units the file does indeed use  
> what must be counted as 11MB of disk space.  This is of course  
> because the block size on the filesystem is 16KB, not 512B, and your  
> 10MB file actually needs 623 filesystem(16KB) units of allocation,  
> i.e. it does actually use more than 10MB of filesystem space.

The output of 'du' includes the indirect blocks, so will be larger
than the filesize for non-trivial files without holes.

        David

-- 
David Laight: david%l8s.co.uk@localhost