[Linux-cluster] newbie: gfs merge

[wolfgang pauli]

> > I installed gfs and all the cluster stuff on our systems and I didn't   
> > have the impression that I missed any of the steps in the manual. So   
> > I have to nodes which both have a gfs partition mounted. I can also   
> > mount these, if I exported them with gnbd. But I don't see the big   
> > difference to nfs yet (apart from maybe performance). I thought that   
> > if I name the gfs-partitions the same (clustername:gfs1) they would   
> > be magically merged or something like that. I thought this was meant   
> > by the notion in the docs that GFS does not have a single point of   
> > failure. Or that we could have redundant file-servers. What did I get   
> > wrong about all that?    
>    
> It sounds like you are a bit confused about what GFS does.  I replied   
> to someone within the last week or so on almost the same issue.  Check   
> the archives.   
>    
> GFS is a filesystem that allows multiple nodes to access and update it   
> at the same time.  The cluster services manage the nodes and try to   
> prevent a misbehaving node from corrupting the filesystem.   
>    
> If you have hard drives in all of your nodes, GFS and the cluster will   
> not help you make them into one big shared storage area -- at least not   
> yet, I believe there is a beta (alpha?) project out there somewhere.   
> If you have a big storage area, GFS and the cluster _will_ allow you   
> to connect all of your nodes to it.   
>    
> The redundancy comes in the fact that you have multiple machines   
> running from the same storage area.  If one of the machines goes down,   
> the others can continue working.  In a load-balanced configuration,   
> the loss of one of the nodes will be transparent to the users.  In   
> theory, of course...  If the storage dies, that's another issue.   
> Hopefully, your storage is raid and can handle a disk failure.   
>    
> --    
> Bowie   
 
Hm... Thanks for you answer! I am definetelly confused a bit. Even after 
reading you post of last week. I understand that i can not merge the file 
systems. Our setup is very basic. We have to linux machines who could act 
as file server and we thought that we could one (A) have working as an 
active backup of the other (B). Is that what the documentation calls a 
failover domain, with (B) being the failover "domain" for (A)? Until now, 
we were running rsync at night, so that if the first of the two servers 
failed, clients could mount the NFS from the other server. There is 
nothing fancy here, like a SAN I guess, just machines connected via 
ethernet switches. So basically the question is, whether it is possible to 
keep the filesystems on the two servers in total sync, so that it would 
not matter whether clients mount the remote share from (A) or (B). Whether 
the clients would automatically be able to mount the GFS from (B), if (A) 
fails.  
  
Wolfgang   

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