ocfs2 is a shared disk clustered filesystem. It allows multiple servers
to r/w concurrently to a volume. It is much more than a simple failover
in the sense that all servers are actively using the volume. And since
it requires a shared disk, the data is always available to all nodes.
So, if you have a shared disk setup, then you can use ocfs2 as the
datastore and use dlmfs to synchronize services between two or more nodes.
http://oss.oracle.com/projects/ocfs2/src/branches/ocfs2-1.2/dlmfs.txt
For e.g., EX holder of resource R starts the services. As only one node
can hold EX on any resource, you can ensure only one node is running
the service. The others will wait for the current holder to die to takeover.
If you don't have a fiber channel, etc. lying around you work place,
look into using iscsi. You will require a third machine to be the iscsi
target. Even enterprise distros are shipping with iscsi initiators (client)
and some even with targets (server).
Other option is to look into drbd. It provides shared disk between two
servers using disk mirroring. While it is not part of mainline kernel yet,
I am hearing more and more of it. Your mileage may vary.
Best of luck.
Sunil
Gregory Machin wrote:> Hi
> I'm looking for a way to mirror data between to servers.
> Where both servers have the same services configured but only some are
> running on the one
> and the remaining are running on the other .. Should one server fail all
> the services become active
> on the one server , and once the issue is resolved and the server is
> back online the services are split up again. This Is easy enough with HA
> etc..
> But I need both servers to mirror each others data, in real time so
> should one go down the other is ready
> to take over, and the process is transparent to the clients / users. And
> when the failed server is started up
> again the data is resynchronized then the services are brought on line
> again.
>
> Eg server 1 provides smtp , pop3 , imap
> server 2 provides mysql, http, dns
>
> If server 1 fails or goes off line server to takes over all roles mysql,
> http, dns and smtp , pop3 , imap
> If server 2 files or goes off line server to takes over all roles smtp ,
> pop3 , imap and mysql, http, dns
> so both servers have to be up to date with each others data, when the
> off line server comes back online
> It needs to syn the difference for all the services that may have
> changed mysql, http, dns, smtp, pop3, imap
> and thus both servers resume normal services.
>
>
> Can ocfs2 do this ?
>
>