On Mon, 14 May 2001, Federico Sevilla III wrote:
> Hi everyone,
>
> While migrating a ReiserFS partition to XFS, I noticed that df reported a
> pretty significant space utilization difference between the two
> filesystems. I transferred my files using two methods, and both had
> identical results.
>
> First I used tar from /xfs: "tar -cl /reiserfs | tar xv", then I used cp:
> "cp -a /reiserfs /xfs". Here is the output when I ran "df -h" after each
> file transfer operation:
>
> Filesystem Size Used Avail Use% Mounted on
> /dev/hda5 2.0G 692M 1.4G 33% /reiserfs
> /dev/hda3 952M 746M 206M 78% /xfs
>
> If this is accurate (although it doesn't seem accurate as I will later
> elaborate), then XFS uses 52MB more than ReiserFS does for a relatively
> small partition (this is actually my root partition, and I only exclude a
> small boot and the home partition).
Do you have tail packing enabled (it is by default).
If you have numerous files smaller then say 4k it will pack more of them
to fill up the spaces.
This results in exactly as much data in a smaller on disk format.
> I decided to check using du by running "du -csm" and found that ReiserFS
> uses 734MB and XFS uses 733MB. This looks more accurate. Would anyone know
> what's wrong with df? It's a much handier tool to use than du, but if it's
> not accurate then it doesn't look like a good tool to use, handy or not.
See above. The actual size of the files stay the same.
Cheers Seth
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