[CI] OpenSSI and CI

[Brian J. Watson]

If I read the docs ok, CI is infrastructure that is useful for more
cluster solutions, not only openssi... correct? Does it make sense
to run CI ALONE, so without another cluster tool 'above' it?

CI is a basic set of cluster building blocks that don't interfere much
with normal kernel operations. Its core feature is a set of APIs for
examining the membership of a cluster and registering to receive a
signal when a node joins or leaves the cluster. CI includes an automatic
heartbeat mechanism to automatically kick a node out if it becomes
unresponsive. It also includes a standardized mechanism for kernels on
different nodes to talk to one another.

OpenSSI builds on CI, but goes much further. It _does_ interfere with
normal kernel operation (in a good way) to create the illusion that your
cluster is a single, giant SMP. Every node shares the same set of
filesystems (including the root), which makes an OpenSSI cluster much
easier to manage than other clusters. You only have one place where you
need to install, upgrade, and configure software. A process on any node
can communicate with processes on any other nodes using ordinary IPC
mechanisms (signals, pipes, semaphores, etc.), which makes it much
easier to develop distributed applications. Processes and TCP
connections can be automatically load balanced across an OpenSSI cluster
to ensure optimal usage of your CPUs. An OpenSSI cluster can be
configured such that any node can fail and the cluster continues running.

OpenSSI provides a general-purpose clustering operating system that can
make things easier for almost everyone who needs a cluster to solve a
particular problem. On the other hand, CI provides some well-tested
building blocks for those few who would prefer to develop their own
clustering solution.

Hope this helps you understand the relationship between the two,

Brian