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[Discuss] Whence distributed operating systems?

nb: I received this Sunday morning. Not sure where the delay was.

On 4/21/2016 10:14 AM, Jack Coats wrote:
> In many ways, we do have a single system signon, with a 'single system
> image' for well developed systems today.

That's not single system image, though, even if it presents the
illusion. Lemme give you a concrete example, one of the last serious
attempts at practical, commercial SSI that I'm aware of: Digital's
Galaxy architecture.

Galaxy was an evolution of VAX/VMS clustering. The idea was to be able
to construct arbitrarily large VAX clusters from what they called quad
building blocks or QBBs. Each QBB was 4 Alpha CPUs and 2GB RAM (IIRC)
and was plugged into a fast fibrecchannel backplane. The prototype I saw
in Nashua was a 4 QBB system.

Galaxy had two configurations. The first was a traditional VAX cluster
with each QBB operating as a single node, so the prototype was a 4 node
cluster with 4 processors and 2GB RAM each. Traditional VAX clusters are
sometimes seen as partial SSI due to the cluster-aware file system (one
of the first ever) and live process migration capabilities (again one of
the first ever).

The second was the namesake galaxy configuration. All of the QBBs were
glommed together into a single large computer. In this configuration,
processes on the prototype saw 1 processor with 16 streams and 8 GB RAM
rather than a 4-node cluster. A processes could allocate more than one
QBB's worth of RAM and not hit swap. It could have threads running on
any or all of the QBBs without having to be programmed specifically for
it. Galaxy was full SSI.

Rich P.

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