[Ocfs2-tools-devel] [PATCH 4/4] Defrag the filesystem

[Joel Becker]

On Mon, Mar 22, 2010 at 08:55:02PM -0700, Joel Becker wrote:
> 1. Making files more contiguous.  This means taking files of many small
>    extents and making them consist of fewer, larger extents.  This is
>    good for performance.
> 2. Making the whole disk more contiguous.  This means packing file data
>    to one end of the disk so that free space is in large hunks.  This is
>    good for future allocation of unfragmented files.

	This is offline defrag.  You can think really big here.  Imagine
this scheme:

Pass 3a: Pack all data to the end of the disk.  Don't care how badly it
         packs, because you're just doing this temporarily.  Now the
         entire front of the disk is empty except for block groups.
Pass 3b: Move data back to the front of the disk to create almost
         completely contiguous files.  Do it in ascending inode order so
         the earliest data extents correspond to the earliest inodes.

Something like that might satisfy both type 1 and type 2 defrag.

Joel

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Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker at oracle.com
Phone: (650) 506-8127