Re: howto preallocate to minimize fragmentation

[Eric Sandeen <sandeen@xxxxxxx>]

Ying-Hung Chen wrote:
> Hi there,
>
> we are storing realtime streaming data (multiple/random writes) in our
> Linux system with XFS filesystem and suffering from heavy fragementation
> (> 90%) . I am wondering what's the best way to reallocate files (say
> 2GB files) before using the file system.
>
> we are creating the 'quick' sparse file like the following: (is this
> cause the problem?)
>
> /bin/dd if=/dev/zero of=/mnt/file.ivf bs=1M seek=2000000 count=1
>
> We are using Linux 2.6.x kernel with XFS filesystem
>
> can anyone help?

See the xfsctl man page from xfsprogs, specifically XFS_IOC_RESVSP

creating a sparse file will not help with fragmentation, unfortunately.

-Eric