[OpenAFS-devel] Re: AFS ... or equivalent ...

[Jeffrey Hutzelman]

--On Monday, January 14, 2008 02:23:47 PM +0000 Robert Watson 
<rwatson@FreeBSD.org> wrote:

> I'd like very much to get at least the kernel parts of an AFS client into
> the base system.

That may well be realistic for arla, though I believe there was a period 
for a while where the kernel/arlad interface was evolving to support 
features like chunking.  I pay only superficial attention to arla-drinkers, 
so I don't know what the status of any of that is; for that, you'd have to 
ask someone who is actively involved in arla development (I believe there 
are some such people on this list).

It is unlikely ever to happen for OpenAFS, in which virtually all of the 
cache manager code is in-kernel and most of it is cross-platform.  Trying 
to pull the OpenAFS cache manager into the FreeBSD kernel would be 
equivalent to forking OpenAFS; what you'd get would work and would keep up 
with FreeBSD, but it would be unlikely to keep up with OpenAFS.

The "let's just slurp everything into the main distribution so we don't 
have to worry about stable interfaces" approach is really poor.  It 
encourages bad engineering practice among people maintaining the main 
distribution, discourages innovation and extension by others, and generally 
doesn't scale.  It's far better to either attempt to maintain stable 
external interfaces to the VFS and VM subsystems, or else admit that you 
don't have the resources to do so given the relatively small number of 
external users, in which case you almost certainly also don't have the 
resources to keep on top of updates to something like OpenAFS.

In the long run, I'm guessing that the OpenAFS cache manager evolves more 
quickly than FreeBSD's VFS interface, which makes pulling the CM into the 
kernel tree a losing battle.  If you disagree, by all means fork that part 
of AFS (or get someone else to do so) and see what happens (AFS's 
user/kernel and RPC interfaces are both fairly stable, so forking just the 
kernel parts should be mostly feasible).

-- Jeff