# The Core-Diameter

Aug 13, 2009, 13:02 (0 Talkback[s])
(Other stories by Douglas Eadline)
"I started to think about this limit and how it would effect the
size of clusters. I did some back of the envelope math to get an
estimate of how c (the speed of light) will limit cluster size. I
want to preface this discussion with a disclaimer that I thought
about this for all of 20 minutes. I welcome variations or
refinements on my ciphering.

"Let’s first consider the speed of light (SOL) in a fiber
cable. The number provided by the Qlogic crew for the webinar was 5
ηs (nanoseconds) to travel one meter in a fiber cable (It
takes light 3.3 ηs to travel one meter in a vacuum). How can
we translate that into a cluster diameter? Latency is measured in
seconds and the SOL is measured in meters per second. Here is one
way. First we have to define some terms:"

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