Filesystem duplication

[Peter Sabaini]

On Monday 20 August 2007 15:43:23 Bart Silverstrim wrote:
> Okay, here's a question for people.  It's kind of long, but please bear
> with me as I could use an idea of what direction to look in for this.
>
> We're on a budget, of course, so that kind of limits solutions available.
>
> I'm looking for a way to duplicate servers storage using Linux.  I'd
> like to have a way to have a file server that, when a system write
> occurs, would be written to 2 different machines.  If one dies, I can
> switch over to the other one (or use heartbeat and high availability to
> have it automatically switch).

Have a look at DRBD 

http://en.wikipedia.org/wiki/DRBD
http://www.drbd.org/

A simple Master/Slave setup should do. 

>
> Ideally I'd be able to have one server in one location and another
> server in another building.

Of course, the speed of the network connection is crucial for the overall 
system performance in such a setup, ie. make sure you have a fast wire 
between those buildings.

hth
peter.


> I know that for some configurations of VMWare, there is a feature touted
> where you can set up (if I understand this correctly) 2 servers to guard
> against hardware failure and if one machine dies, the other one will
> pick up the first one's virtual machine load and kick over, but this
> still relies on a third computer to act as a NAS.  What happens if the
> NAS needs updating or has a failure?  Wouldn't it all die?
>
> So I'd like to get a configuration built that would run a virtual server
> in one building and a storage system to go with it, and another server
> and storage server in another building, but that would still rely on
> data getting synced between the two storage servers.  If I don't have
> auto-migration, I could at least hope to have some form of the virtual
> drives duplicated and can manually start them if need be.
>
> Is anything like that available?
>
> Or am I simply going to have to start looking at only having redundancy
> on the execution server, and the NAS hardware can only be backed up in
> some other fashion?
>
> How do other admins deal with this situation?
>
> Are there any filesystems that are tested and reliable that work under
> Ubuntu for writing data between two machines to act as a "virtual
> server," or better yet a howto resource for HA that would allow such a
> configuration that also includes what's necessary for the cloning of the
> MAC address, the IP switchover, etc...?
>
> And could such a configuration be done using 2 or 3 Linux systems, or
> would it also rely on dedicated special hardware/switch configurations?
>
> Thank you,
> -Bart