Arch Linux

earlz

Member

Registered: 2010-07-11

Posts: 39

df reports 380G of space used, du reports 200G of space used

Hello, I'm aware of the many differences between df and du, and how it can skew numbers a bit between them. However, I have an XFS volume that has a huge amount of skew. du -h reports everything as using 200G of space, while df -h reports 380G of space. This volume has been used to hold very large files (VM harddrive images), if that may cause such a problem. I need to know why the numbers are so far apart, and also which one actually indicates how much space I can use. If I try to create a 250G file, would it fail or succeed?

alphaniner

Member

From: Ancapistan

Registered: 2010-07-12

Posts: 2,810

Re: df reports 380G of space used, du reports 200G of space used

Maybe try du with the --apparent-size flag.

FTR I've never used it; I thought your VM disk images could be sparse files and it came up when I searched the du manpage for 'sparse'.

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karol

Archivist

Registered: 2009-05-06

Posts: 25,440

Re: df reports 380G of space used, du reports 200G of space used

Does this fs has some special tools for measuring the used space?
http://unix.stackexchange.com/questions … -the-files

nomorewindows

Member

Registered: 2010-04-03

Posts: 3,408

Re: df reports 380G of space used, du reports 200G of space used

Are his volumes on different partitions?

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x33a

Forum Fellow

Registered: 2009-08-15

Posts: 4,587

Re: df reports 380G of space used, du reports 200G of space used

Give ncdu a try, and see what difference (if any) is shown for the values of "Total disk usage" and "Apparent size".

earlz

Member

Registered: 2010-07-11

Posts: 39

Re: df reports 380G of space used, du reports 200G of space used

Maybe try du with the --apparent-size flag.

FTR I've never used it; I thought your VM disk images could be sparse files and it came up when I searched the du manpage for 'sparse'.

I tried --apparent size. That says 229G, so a bit closer to expected. Also, some VM disk images are not sparse purposefully. if a disk image is not sparse, and fairly unfragmented on disk, then you gain a major performance advantage with VM disk performance

ncdu reports similar to du with apparent size. It reports both apparent size of 228.8G and total disk usage of 228.4G