Re: I/O hang, possibly XFS, possibly general

Dave Chinner
2011-06-08T05:18:48Z

On Tue, Jun 07, 2011 at 03:09:09PM +0100, Peter Grandi wrote:
> Personally I'd rather have a file system design with space
> reservations (on detecting an append-like access pattern) and
> truncate-on-close than delayed allocation like XFS;

Welcome to the 1990s, Peter. XFS has been doing this for 15 years.
It is an optimisation used by the delayed allocation mechanism,
not a replacement for it. You might have heard the term
"speculative preallocation" before - this is what it does.

FYI, ext3 has a space reservation infrastructure to try to ensure
contiguous allocation occurs without using delayed allocation. It
doesn't work nearly as well as delayed allocation in ext4, btrfs or
XFS...

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com