Re: Filesystem fragmentation and scatter-gather DMA

[Andreas Dilger <adilger sun com>]

On Mar 16, 2008  15:13 -0500, William Tambe wrote:
> When designing a filesystem, is fragmentation really an issue if
> access to the disk can be done using scatter-gather DMA techics ?

Yes!!!  Scatter-gather only handles "fragmentation" in memory, where
seek time is zero.  If there is fragmentation on disk you pay 8ms
for each fragment in the read.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.