If such a thing exists, I've been hoping to build a cluster of virtual servers that work very much like they are one physical machine, but that work without the requirement of MPI or other message-enabled S/W. SSI seems like a term that implies this. And if I understand Kerrighed correctly, it serves this purpose.

What I don't require is a cluster where the work of a single process is divided among the physical machines and their processors.

What I do need is a cluster where the work of a single (perhaps virtualized ) server or service is divided among those physical machines.

Though it may be true in the case of many services that these are the same two things.

Example: if I had an application that used an SQL server, traditional round-robin type load balancing couldn't really work. After all, without cluster-aware code in front of the sql daemon, first server in the pool to open a database file would have a lock on that file until it was bloody well good and ready to let go. Thus other physical servers couldn't simultaneously access the same area of the database.

Does Kerrighed (or any other cluster solution) do this? How stable has it been in your experience? How much overhead and maintenance was involved?

Expiring minds want to know...