Current status of nullfs and/or unionfs?

[EirikØverby]

Hi all,

I'm struggling with some hosting environments where I am managing a large
number of jails (>100) spread over about a dozen servers. I am starting to
see disk space as a real problem, especially given that each physical box
needs to be autonomous - i.e. I can't rely on any external storage, and I am
limited to 1U and 2U servers.

The solution, or at least parts of it, would be to have certain parts of the
jail filesystems mounted in via nullfs (acceptable solution) or unionfs
(ideal solution). However, ever since FreeBSD 4.10 this has been a major
problem, as both filesystems started exhibiting major stability and data
integrity issues.

Before I start playing with this again, I'd like to know if any work has
been done on either of these in 5.x. Specifically, I'm currently running
5.3-p6 or newer on all the systems, and as of yesterday I've been using
5.4-prerelease (cvsup) on a couple of test systems.

What can I expect to see when trying nullfs and/or unionfs today? Has
anything changed? Do I have even a remote chance of making it work - and if
it doesn't work, what are my chances of anyone having time or energy to look
into it? I'm an admin only, no coder, otherwise I'd be happy to look into it
myself.

Thanks,
/Eirik