[OpenAFS] more newbie questions

Jonathan Dobbie jonathan_dobbie@mcad.edu
Thu, 22 Feb 2007 16:32:11 -0600

Thank you for the responses, we're still designing our storage system  
and AFS still seems like the best option.  I've installed AFS on a  
test server (G4 OSX - I figured I'd start with the craziest platform  
we might want it on)

I'm hoping that if I toss my plan out now, people can point out the  
holes before I invest too much time in it.  The end goal is uptime  
more than performance.

Our AFS servers would probably all be running linux.  Clients are  
OSX, windows and Linux.

There would be an MSKDC that would trust the main MIT KDC.  I need to  
talk to the Windows Admin about ntlm, but if we need to sync the  
passwords, thats fine (password change is done via a webpage or  
command line tools that we wrote, not passwd), if not, the MSKDC will  
have random passwords.

We only have one small chunk or data that (I think) lends itself to a  
RO replica.  We have a network library that it automounted by all osx  
computers.  All other data is updated enough that people wouldn't  
want to wait for me to release  it.  Am I missing a way to set up RO  
replicas?  I'd be nice if they would mirror changes automatically.   
Part of what I want is to be able to have any one piece of hardware  
die, and either route around it automatically, or bring it back up  

Here is my current idea (I'm not hugely fond of it, so I'm really  
hoping that someone has a better one)  There will be two FC storage  
devices (we currently have one xraid.  If we can't get much cash,  
it'll be another, if not, something better.)  These will be kept in  
sync with DRBD, at least at the partition level (which seems a little  
silly)  Heartbeat will be used so that if anything goes wrong with  
the server or the storage, the other server will restart its AFS  
server and start serving the downed server automatically.  (It'll  
certainly end up more complicated than this, but that's the basic idea).

Could someone please point out the holes in this plan?  Is there a  
simpler way to do this with R/O replicas that might require me to  
manually promote the replica to R/W, but would be less error prone?   
Most of the data involved is home directories and departmental  
shares.  If it can be fixed remotely in <5 minutes, it's probably  
good enough.

I keep thinking that there should be a clever way to use GFS(not  
google, the RH one) instead or DRBD to keep the volumes in sync.  All  
of the machines have two gigabit NICs, but it still seems like a  
waste not to use FC.

More precisely, would this be possible:
/vicepd is on GFS on both RAID arrays (A and B)
it's mounted on servers 1(rw) and 2(ro).
If A dies, B serves the data and no one notices
if 1 dies, heartbeat promotes 2 to rw and ro.
and, if it is possible, what would users notice?

As a last question, completely out of left field, does anyone know if  
AFS stores apple metadata?  I've seen some references to it doing so  
in Apple Double files, but nothing concrete.

Thank you for your help

Jonathan Dobbie
Academic System Administrator
Minneapolis College of Art and Design.