[H-GEN] Best FS for use with multiple Unix variants

[Greg Black]

I have some external HDDs (both eSATA and USB) that I use for
additional backups of data on my home network.  The machines on
the home network run a mix of FreeBSD (UFS), Linux (ext2, ext3),
Mac OS-X (HFS+) and Solaris (ZFS).

What I need is an on-disk FS that I can use that will allow all
those systems to both write and read the external disk.  Since
some of the machines are limited to USB, the result has to work
for an external USB disk.

If anybody has an answer and preferably the utility and OS to
use to setup the disk in the first place, I'd be grateful for
pointers.

This is not an invitation to speculate, as I can do that myself
and have already done quite a bit of it without a useful
result.  Please reply direct to me.  I will provide a summary of
the information to the list when I have a result.

Greg