Block device over network from Linux to FreeBSD

[Martin Cracauer]

All right, here's a question that'll make your IQ drop by 5 points
just from pondering it :-)

What's the best way to provide, over the network, a block device on
harddrives that live on a Linux box and "export" them to a FreeBSD
machine? Aka I want a FreeBSD filesystem on harddrives that are
physically in a Linux box.

Long story:

My backup strategy is a FreeBSD filesystem with snapshots on a bunch
of harddrives that live on networked computers in the basement.  All
these computers boot diskless or disky into a variety of OSes, usually
Linux or FreeBSD.  It would be easy to just use ext2fs or another
filesystem supported by both, but I'd really like ufs2 snapshots.  So
I need to access the disks in a box running Linux as a block device
from a machine running FreeBSD.  When the machine having the physical
disks runs FreeBSD I want to access the same raw devices directly, of
course.

The brute-force approach would be:
- ext2fs on disks
- files inside ext2fs for use via mdconfig (and ccd)
- then, depending on OSes booted, either:
  - export via NFS and mdconfig on NFS mounts on remote FreeBSD machine
  - direct FreeBSD mount (machine runs FreeBSD)

Another alternative I see is VMware or if any of the free emulators
can boot FreeBSD on Linux and use the disks directly in the guest OS.

Linux has a network layer for block devices:
http://www.it.uc3m.es/ptb/nbd/ . On first sight, it doesn't look too
exiting nor does it look straightforward to implement a client in
GEOM.  It uses daemons on both ends, so failover will not exactly be
an improvement over NFS.  At least with NFS you know that a lot of
other people depend on what you write being delivered eventually.

Then there's ATA over Ethernet as an established protocol.

Any other ideas?

USB'ing the harddrives is not considered sportish :-)

Martin
-- 
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Martin Cracauer <cracauer at cons.org>   http://www.cons.org/cracauer/
FreeBSD - where you want to go, today.      http://www.freebsd.org/