[OpenAFS] mount points and replication problems

[Cédric CACHAT]

Thanks for your precisions, Frank
I did not mount my home directories with de -rw option, now I understand 
why it is important. I'll try it tonight.
I have understood, thanks also to Todd, Horst and Jeffrey that there is 
little point in replicating home directories since they change quite 
often, I think backing them up will be enough (in case of data loss).
But I've seen how great AFS is for authentication since I can used my 
Kerberos REALM provided by MIT Kerberos V. It took me some time to tune 
the two components so they might work together. Now that they are, I'll 
keep AFS even if I was expecting so much more... (thats is because I 
don't contribute to AFS's programming, and you know how clients are 
never happy, they always expect more than what's reasonable ;-) ) So 
keep up the good work.

Thank you all for your quick help.

Cédric

Frank Burkhardt a écrit :

>Hi,
>
>On Tue, Jul 12, 2005 at 01:17:05PM +0200, C?dric CACHAT wrote:
>  
>
>>Hello,
>>
>>this is the first time I write and I am pretty new to AFS. I have a 
>>question regarding mount points in AFS.
>>Here is what I'm trying to achieve:
>>I want all my users to have their home directory in AFS, the plan is to 
>>set an AFS tree looking like:
>>/afs/cell/usr/homes/<user1>
>>I created the following volumes on my primary server:
>>root.afs
>>root.cell
>>common.usr
>>common.homes
>>user.user1
>>and then I mounted them using the fs command :
>>*# fs mkm /afs/cell/usr common.usr* and so on... (I didnt use *# fs mkm 
>>/afs/_._cell/usr common.usr *maybe my problem comes from here?)
>>So far everything is under control.
>>    
>>
>
>Did you explicitely mount the RW-instance of the homedirectory-volumes?
>
>-> fs mkm /afs/cell/usr/homes/user1 user.user1 -rw
>                                               ===
>
>Otherwise you would have RW-acces to the homdirs only if there are
>no RO-copies.
>
>  
>
>>Since I have many sites, I have set up one AFS server on each site. 
>>Because all users don't work on the same site I decided to create user.* 
>>volumes on their closest server, so I created volume user.user1 on the 
>>primary server and user.user2 on the secondary server.
>>Without any replication it works perfectly if BOTH servers are running. 
>>If one is down, say the master, then acces to a user's home-dir is 
>>impossible.
>>Thats's were it's getting complicated for me: I then set up replication 
>>to the second site so that I have:
>>
>>primary server 	secondary server
>>root.afs (RW) 	root.afs (RO)
>>root.cell (RW) 	root.cell (RO)
>>common.usr (RW) 	common.usr (RO)
>>common.homes (RW) 	common.homes (RO)
>>user.user1 (RW) 	user.user1 (RO)
>>user.user2 (RO)
>>	user.user2 (RW)
>>    
>>
>
>You most probably want to have RO-copies of "structural volumes" like
>root.afs, root.cell, common.usr, common.homes on both fileservers.
>
>  
>
>>Looking at the array above, if the primary server is down, user1 should 
>>be able to access is home dir but Read Only whereas user2 should be able 
>>to read/write to his home directory.
>>    
>>
>
>No. user.user2 resides on primary-server so user2 will have no access at all.
>
>
>
>  
>
>>That's exactly what I want.
>>The problem is user2 can only read and not write (il I try ls 
>>    
>>
>
>See '-rw' -option of 'fs mkm'.
>
>  
>
>>/afs/.cell, it hangs then says timeout). Is it normal or did I miss a thing?
>>Second question, I don't know what to set their homedirectory to (read 
>>from LDAP at login), do I have to use /afs/_cell_/usr/homes/user1 or 
>>/afs/_.cell_/usr/homes/user1.
>>    
>>
>
>The first. There should be no "dot-path-component" in a user's homedir as long
>as you mount the homedir-volume '-rw'.
>
>  
>
>>If I use the former, when both servers are running they can't write to 
>>their directory, they have to cd to /afs/.cell/usr/homes/user1 in order 
>>to write which is not practical; if I use the latter, it works all right 
>>when both servers are running but when the primary is down, it fails to 
>>acces the home directory (server timeout, the branch /afs/.cell is down).
>>    
>>
>
>That's expected behaviour because root.cell(RW) (aka. /afs/.cell) resides
>on primary-server.
>
>  
>
>>Did someone ever try to set up such a network, or is it impossible? 
>>    
>>
>
>Impossible is to automagically switch a user's homedir to RO when there's
>no RW-volume available. That's because the '-rw'-switch forces the AFS-client
>to mount the RW-volume - *without* any fallback to RO.
>
>  
>
>>Could you tell me then how should I mount my tree?
>>    
>>
>
>/afs                 root.afs
> |- cell             root.cell
> |  `- home          homes
> |     `- user1      user.user1(-rw)
> |- .cell            root.cell(-rw)
> |  ...
>
>  
>
>>I think my problems come from the .cell and cell, I don't quite 
>>understand the impact it has on the rest of the tree.
>>    
>>
>
>Whenever you want to i.e. add a user, just access /afs/.cell/home,
>add the mountpoint and 'vos release' the homes-volume.
>
>All volumes along the path (root.afs, root.cell, homes) should have
>RO-instances on both fileservers.
>
>Your users needn't access .-paths.
>
>Regards,
>
>Frank
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>  
>