[Samba] about samba failover

[steve]

On Sat, 2014-06-28 at 21:50 +0200, Davor Vusir wrote:
> 2014-06-28 20:16 GMT+02:00 steve <steve at steve-ss.com>:
> > On Sat, 2014-06-28 at 20:02 +0200, Davor Vusir wrote:
> >
> >>
> >> Never the less, domain based DFS works. Thanks to Garming, if I recall
> >> correctly.
> >
> > Hi
> > That's exactly what we want. Two domain file servers carry the same
> > share. One goes down, there's still another left with the same share.
> >
> > Can you point us at a howto?
> > Thanks,
> > Steve
> >
> >
> 
> Hi!
> 
> I haven't found a howto. If you can't Explore to
> \\example.org\netlogon, I suggest you revert to Ubuntu 12.04 for
> starters. :) 

Yes, but that's as far as it goes. We can only see the shares on the DC,
but only netlogon and sysvol. If we create our own share, it does not
show. Neither do any other shares on the dfs root we have set on our
file server. We _always_ have to specify the file server, so domain dfs
does not work.


> 
> According to the documentation
> (https://www.samba.org/samba/docs/man/Samba-HOWTO-Collection/msdfs.html),
> it is not possible in my opinion. At least not with automatic
> failover. Because there is not enough information embedded in Sambas
> implementation that informs the (Windows) client which server is to
> prioritize and which is secondary and for how long this information is
> valid. You can create links to several shares but you can't determine
> which server the client will connect to (if it does not connect
> alphabetacally(?)). If client A connects to server A the first time,
> and client B connects to server B, you have to implement two-way
> synchronization. There is no way to determine if the opposite occurs
> at the next logon. The documentation fails to tell.
> 
> The only thing you know is that domainbased DFS is possible. The
> availability solution is for you to decide.
> 
> I think it boils down to a solution with one (1) link to either a cold
> stand-by server or a hot stand-by server(cluster) of some sort.
> 
> If you choose the cold stand-by solution, you'll have to 'relink' to
> the stand-by server manually in case of server crash. Does rsync copy
> open files? How often is enough? Every five minutes? Or is inotify
> (http://www.kutukupret.com/2011/06/28/postfix-one-way-maildir-replication-backup-using-inotify-and-rsync/)
> good enough?
> 
> If you choose the hot stand-by solution, I think DRBD will be satisfactory.
> 
> With the first solution you will loose data/information. The second
> guaranties consistency.
> 
> The trick is one link to one server. High avaliability not included.
> 
> Regards
> Davor