Libguestfs - Oct 2014 - [PATCH nbdkit] streaming plugin: Add support for a sliding window

[Sorry, can't use git-send-email at the moment ...]

These patches implement a sliding window for the streaming plugin[1]
in nbdkit.

I would like to be able to stream a filesystem from tools such as
'virt-make-fs'[2].  This is a fairly frequently requested feature.

Unfortunately:

(a) The patches make the code significantly more complex and therefore
likely to have bugs.

(b) They are not practically useful.  'parted' likes to write to the
beginning and end of a disk, even when creating a simple MBR, and of
course 'mkfs' scribbles the group headers across the whole disk when
creating a filesystem.

A simple window approach is obviously not sufficient.  A better
approach might be something like a sparse, size-limited map recording
writes at any point in the disk.  But that has the problem that you
don't know when you can commit a write to the stream -- some heuristic
would have to be used.

I'm posting them to the mailing list for the record and in case anyone
has any better ideas.

Rich.

[1] http://rwmj.wordpress.com/2014/10/14/streaming-nbd-server/#content
[2] http://libguestfs.org/virt-make-fs.1.html

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
Fedora Windows cross-compiler. Compile Windows programs, test, and
build Windows installers. Over 100 libraries supported.
http://fedoraproject.org/wiki/MinGW