The first issue that I can spot is that I believe DRBD only supports 2 machines per volume at most. Now, you could probably work out some sort of combo DRBD + software RAID arrangement that would let you get it onto all four machines, but you may end up with issues with the data sync'ing correctly. Network-attached storage is very, very easy to come by these days - you can pick up a simple, two-disk mirroring device that supports NFS (and sometimes even iSCSI) for a few hundred USD. Maybe this is out of the question - no idea what sort of a budget you're going on here, but getting something like that would alleviate the problem of getting more than just two of the PCs synchronized with DRBD.
It looks like the company that sponsors DRBD, LINBIT, has a commercial offering of it that supports synchronization with more than two machines.
-Nick
>>> "Rudi Ahlers" <rudiahlers@xxxxxxxxx> 2008/12/03 02:08 >>> Hi all,but I want to start experimenting with clusters, and I would like to use normal desktop grade hardware for this. I have some extra PC components lying around, enough to build 3 - 4 moderate desktops with a PIV / C2D CPU & 512MB - 1GB RAM each. All the machines should have at least a 100MB NIC, but I can add a gigabit NIC to the machines that doesn't have it if need be.
I have used Linux Heartbeat to failover a MySQL cluster before, and it's actually been running very well for about 3 years now. But, I want to start looking @ total clustering, with DRBD - where everything (not just MySQL) is being replicated across the 4 machines. I'm also intereated in load balancing.
Has anyone done anything like this?
The cluster will be running / hosting a few XEN Virtual Machines, and idealy if one PC / server dies (hardware failure / power failure / etc), then on of the other machines should still be running the virtual machines, i.e. no downtime. Is this possible? Can somone steer me into a direction where I can get more info on this?
My aim: to use common, cheap PC equipment & CentOS for the project, I don't want to spend any more money, and want to use what I have.
--
Kind Regards Rudi Ahlers
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