Re: [9fans] off-wall idea, file server and SAN

[anothy@cosym.net]

i'm not entirely sure i understand your question, but here's a pass
at a reply anyway. if i'm off the mark entirely, just ignore me.

a "proper" plan 9 network consists of a seperate file server and cpu
server (maybe more, and probably some terminals). the file server is
designed to do one thing: serve the cpu servers (and terminals)
their file systems. any additional services, like dhcp/bootp and
tftp, also useful for booting, are provided by cpu servers. in that
spirit, i'd expect the "Plan 9 answer" to your question to be that
you'd implement whatever other file services you're looking for on
the cpu servers. you'd then run that service on the cpu server (most
likely in /bin/cpurc), and have clients look to that cpu server for
their service.

as an example, Plan 9 ships with a NFS server (and associated
utilities) that allow you to point Unix boxes (or pc's with NFS
clients) at a Plan 9 cpu server for file service. i've run
heterogeneous network with Plan 9 as the core and various different
Unix flavors talking to it (making backups, typically the worst part
of any Unix admin's job, a non-issue). it worked well, but not
perfectly (see below). but if you're looking for a protocol that's
not already there, the nfs server may be a good place to start.

i have a vauge recolection of someone working on an SMB server, but
i've never had a need for it and don't really remember if it ever saw
the light of day. anyone? other protocols, like Appletalk or whatever
you need, could be written in the same way: as user-level code for a
plan 9 cpu server. much easier than builing it into the file server.

note that there are flaws to the approach: you have to translate the
requests from NFS (or whatever) into 9p, which takes some time. for
casual use, it's not such a big deal, but it gets notably slow with
heavy load. also, the authentication schemes don't match, which can be
awkward. the Plan 9 nfs server provides a special hack for doing
netkey authentication, but it's definatly a hack. the hack can be
automated into the login process or something, but it's still ugly. but
it does work. and i think the general feeling (and certainly mine) is
that these flaws are well worth it to avoid including various protocols
(and thus additional complexity and posability for bugs) into the file
server, the part of the network where stability is most key.

note also that i know nothing about the "new" file server being
developed - it may make all these points false or obsolete, i don't
know. this is based on the current file server. the new 9p may also
address some of the authentication issues. again, i don't know.
-α.