<s>
The	O
history	B-Operating_System
of	I-Operating_System
computer	I-Operating_System
clusters	I-Operating_System
is	O
best	O
captured	O
by	O
a	O
footnote	O
in	O
Greg	O
Pfister	O
's	O
In	O
Search	O
of	O
Clusters	O
:	O
“	O
Virtually	O
every	O
press	O
release	O
from	O
DEC	O
mentioning	O
clusters	O
says	O
‘	O
DEC	O
,	O
who	O
invented	O
clusters	O
...	O
’	O
.	O
</s>
<s>
The	O
formal	O
engineering	O
basis	O
of	O
cluster	O
computing	O
as	O
a	O
means	O
of	O
doing	O
parallel	O
work	O
of	O
any	O
sort	O
was	O
arguably	O
invented	O
by	O
Gene	O
Amdahl	O
of	O
IBM	O
,	O
who	O
in	O
1967	O
published	O
what	O
has	O
come	O
to	O
be	O
regarded	O
as	O
the	O
seminal	O
paper	O
on	O
parallel	O
processing	O
:	O
Amdahl	B-Operating_System
's	I-Operating_System
Law	I-Operating_System
.	O
</s>
<s>
Amdahl	B-Operating_System
's	I-Operating_System
Law	I-Operating_System
describes	O
mathematically	O
the	O
speedup	O
one	O
can	O
expect	O
from	O
parallelizing	O
any	O
given	O
otherwise	O
serially	O
performed	O
task	O
on	O
a	O
parallel	O
architecture	O
.	O
</s>
<s>
Packet	B-Protocol
switching	I-Protocol
networks	O
were	O
conceptually	O
invented	O
by	O
the	O
RAND	B-Application
corporation	O
in	O
1962	O
.	O
</s>
<s>
Using	O
the	O
concept	O
of	O
a	O
packet	B-Protocol
switched	I-Protocol
network	I-Protocol
,	O
the	O
ARPANET	O
project	O
succeeded	O
in	O
creating	O
in	O
1969	O
what	O
was	O
arguably	O
the	O
world	O
's	O
first	O
commodity-network	O
based	O
computer	O
cluster	O
by	O
linking	O
four	O
different	O
computer	O
centers	O
(	O
each	O
of	O
which	O
was	O
something	O
of	O
a	O
"	O
cluster	O
"	O
in	O
its	O
own	O
right	O
,	O
but	O
probably	O
not	O
a	O
commodity	B-Operating_System
cluster	I-Operating_System
)	O
.	O
</s>
<s>
It	O
also	O
established	O
the	O
paradigm	O
in	O
use	O
by	O
all	O
computer	O
clusters	O
in	O
the	O
world	O
today	O
—	O
the	O
use	O
of	O
packet-switched	B-Protocol
networks	I-Protocol
to	O
perform	O
interprocessor	O
communications	O
between	O
processor	O
(	O
sets	O
)	O
located	O
in	O
otherwise	O
disconnected	O
frames	O
.	O
</s>
<s>
The	O
development	O
of	O
customer-built	O
and	O
research	O
clusters	O
proceeded	O
hand	O
in	O
hand	O
with	O
that	O
of	O
both	O
networks	O
and	O
the	O
Unix	B-Application
operating	I-Application
system	I-Application
from	O
the	O
early	O
1970s	O
,	O
as	O
both	O
TCP/IP	B-Protocol
and	O
the	O
Xerox	O
PARC	O
project	O
created	O
and	O
formalized	O
protocols	O
for	O
network-based	O
communications	O
.	O
</s>
<s>
The	O
Hydra	B-Application
operating	I-Application
system	I-Application
was	O
built	O
for	O
a	O
cluster	O
of	O
DEC	B-Device
PDP-11	I-Device
minicomputers	O
called	O
C.mmp	B-Operating_System
at	O
Carnegie	O
Mellon	O
University	O
in	O
1971	O
.	O
</s>
<s>
However	O
,	O
it	O
was	O
not	O
until	O
circa	O
1983	O
that	O
the	O
protocols	O
and	O
tools	O
for	O
easily	O
doing	O
remote	O
job	O
distribution	O
and	O
file	O
sharing	O
were	O
defined	O
(	O
largely	O
within	O
the	O
context	O
of	O
BSD	B-Operating_System
Unix	I-Operating_System
,	O
as	O
implemented	O
by	O
Sun	O
Microsystems	O
)	O
and	O
hence	O
became	O
generally	O
available	O
commercially	O
,	O
along	O
with	O
a	O
shared	O
filesystem	B-Application
.	O
</s>
<s>
The	O
first	O
commercial	O
clustering	O
product	O
was	O
ARCnet	B-Protocol
,	O
developed	O
by	O
Datapoint	O
in	O
1977	O
.	O
</s>
<s>
ARCnet	B-Protocol
was	O
not	O
a	O
commercial	O
success	O
and	O
clustering	O
per	O
se	O
did	O
not	O
really	O
take	O
off	O
until	O
Digital	O
Equipment	O
Corporation	O
released	O
their	O
VAXcluster	B-Operating_System
product	O
in	O
1984	O
for	O
the	O
VAX/VMS	B-Operating_System
operating	O
system	O
.	O
</s>
<s>
The	O
ARCnet	B-Protocol
and	O
VAXcluster	B-Operating_System
products	O
not	O
only	O
supported	O
parallel	O
computing	O
,	O
but	O
also	O
shared	O
file	B-Application
systems	I-Application
and	O
peripheral	O
devices	O
.	O
</s>
<s>
VAXcluster	B-Operating_System
,	O
now	O
VMScluster	B-Operating_System
,	O
is	O
still	O
available	O
on	O
OpenVMS	B-Operating_System
running	O
on	O
Alpha	O
,	O
Itanium	O
and	O
x86-64	O
systems	O
.	O
</s>
<s>
No	O
history	O
of	O
commodity	O
computer	O
clusters	O
would	O
be	O
complete	O
without	O
noting	O
the	O
pivotal	O
role	O
played	O
by	O
the	O
development	O
of	O
Parallel	B-Operating_System
Virtual	I-Operating_System
Machine	I-Operating_System
(	O
PVM	B-Operating_System
)	O
software	O
in	O
1989	O
.	O
</s>
<s>
This	O
open	B-Application
source	I-Application
software	I-Application
based	O
on	O
TCP/IP	B-Protocol
communications	O
enabled	O
the	O
instant	O
creation	O
of	O
a	O
virtual	B-Architecture
supercomputer	I-Architecture
—	O
a	O
high	O
performance	O
compute	O
cluster	O
—	O
made	O
out	O
of	O
any	O
TCP/IP	B-Protocol
connected	O
systems	O
.	O
</s>
<s>
Free-form	O
heterogeneous	O
clusters	O
built	O
on	O
top	O
of	O
this	O
model	O
rapidly	O
achieved	O
total	O
throughput	O
in	O
FLOPS	O
that	O
greatly	O
exceeded	O
that	O
available	O
even	O
with	O
the	O
most	O
expensive	O
"	O
big	B-Architecture
iron	I-Architecture
"	O
supercomputers	B-Architecture
.	O
</s>
<s>
PVM	B-Operating_System
and	O
the	O
advent	O
of	O
inexpensive	O
networked	O
PCs	O
led	O
,	O
in	O
1993	O
,	O
to	O
a	O
NASA	O
project	O
to	O
build	O
supercomputers	B-Architecture
out	O
of	O
commodity	B-Operating_System
clusters	I-Operating_System
.	O
</s>
<s>
In	O
1995	O
the	O
Beowulf	B-Operating_System
cluster	I-Operating_System
—	O
a	O
cluster	O
built	O
on	O
top	O
of	O
a	O
commodity	O
network	O
for	O
the	O
specific	O
purpose	O
of	O
"	O
being	O
a	O
supercomputer	B-Architecture
"	O
capable	O
of	O
performing	O
tightly	O
coupled	O
parallel	O
HPC	B-Architecture
computations	O
—	O
was	O
invented	O
,	O
which	O
spurred	O
the	O
independent	O
development	O
of	O
grid	B-Architecture
computing	I-Architecture
as	O
a	O
named	O
entity	O
,	O
although	O
Grid-style	O
clustering	O
had	O
been	O
around	O
at	O
least	O
as	O
long	O
as	O
the	O
Unix	B-Application
operating	I-Application
system	I-Application
and	O
the	O
Arpanet	O
,	O
whether	O
or	O
not	O
it	O
,	O
or	O
the	O
clusters	O
that	O
used	O
it	O
,	O
were	O
named	O
.	O
</s>
