[OpenAFS] how?: Distribute /home to n Terminal Servers

[Steve Wright]

Dan Pritts wrote:

Hi Dan,

I am subscribed to the list, so replying to the list only will be fine.  8-)

For multiple Terminal Servers, we have been NFS mounting /home on a 
dedicated machine.  That is, none of the terminal servers actually 
*have* a /home partition.  All Servers `mount /home -t nfs 
<remote-machine>/home/`.


We are looking at an alternative because ;

a.  A backend /home NFS Server is a single point of failure, and it is 
not easy to have this 'mount' failover in case this machine faults.

b.  The NFS Server is an unnecessarily 'extra' box, when the same 
functionality could be provided by a distributed filesystem between 
existing Terminal Servers.

c.  It is simpler.  The installed, complete system will be distributed 
as a ISO Set, so there will be very few AFS configuration for the 
sysadmin to deal with.

The load-balancer will direct a login attempt to any one of the desktop 
servers and users would expect to have their account act as normal, with 
all their files intact.

At the next login attempt, the same user may end up logged-in to an 
entirely different machine, with different DFS cache contents, but we 
need the  /home/<user>/* contents to be ready-synced for them to use.

I have examined all sorts of solutions over the last two months, 
including `rsync`ing /home/<user>/* to all other machines on "user 
logout", Intermezzo DFS, CODA DFS, and now I wish to test and examine a 
solution with OpenAFS.

Please do tell me right away if I am entirely mis-directed.  8-)


>*every* machine that wants to access files that live in /afs needs to
>be an afs client.  This includes AFS server machines. 
>

ok.  Since we have a small number of machines, what would be the 
situation running *all* (max 10) machines as AFS Servers, and then 
acting as their own clients,

>
>
>For your configuration, I woudl recommend a single AFS file & db server,
>which may or may not also be one of your XDMCP servers (i would tend
>to have it on a separate machine).  
>

ok.  Will the clients still sync if the server is down ?  Will we still 
have our single point of failure ?  Can more, or all of the Terminal 
Servers act as OpenAFS Servers, as well as a client for the cell ?  Can 
we then `mount` this cell as /home ?

>
>Depending on what it is that you are trying to get by using AFS (eg,
>access across multiple sites/client side caching, or security, or
>what), you may find that NFS is sufficient for your needs.  
>

We simply want 2-10 Terminal/Application Servers that keep /home/* + 
UIDs + GIDs sync'ed at all times.  All these Terminal/App Servers are on 
the same physical Ethernet Segment, firewalled in, on one site, and 
probably in the same rack - although it would be nice to distribute 
across the complex/campus near their associated set of Terminals.

>
>You will definitely find that NFS is easier to set up and administer.
>

Oh Yes.  I agree.  But that functionality is limiting us now, and we 
wish to move on.



Any and all comments would be most welcome.


TIA,
Steve