[TUHS] History repeating itself

Michael Kjörling michael at kjorling.se
Sun Jul 31 01:30:36 AEST 2016


On 30 Jul 2016 10:15 -0400, from cowan at mercury.ccil.org (John Cowan):
>> Who needs FedEx?  
> 
> Well, latency counts for something too, as does radius: if I want to
> send bulk data from New York to London (a very normal thing to do),
> your station wagon isn't going to count for much.

You could, however, get an economy class flight ticket and load up
your suitcase with either HDDs or SDXCs (I suspect SDXCs would be
better per amount of data from the perspective of both volume and
weight, and would take better to handling). Given FedEx's prices,
_once you have the infrastructure set up_ (which you'll need whether
you have someone travel with the media, by air or by stationwagon, or
FedEx it), that _might_ even compare favorably in terms of bytes
transferred per second per dollar. (Now that's a measurement of
throughput I don't think I've seen before; B/s/$.) Of course, you'd
need someone who can babysit the suitcase, which potentially adds to
the cost, but the stationwagon traditionally hasn't been self-driving
either, and most of a transatlantic flight isn't active time on part
of the person travelling with the suitcase so you could go with an
overnight flight and allow the person to sleep.

If you want to reduce the risk of the bag getting handled roughly or
lost in handling, reduce the above to carry-on luggage; it will still
provide a quite respectable throughput.

If carry-on allows 10 kg (it's been quite a while since I flew
commercially) and a SDXC card that can store 200 GB weighs 5 grams
(seems a reasonable back-of-the-napkin estimate), that would allow
approximately 200 GB * 2,000 = 400 TB transferred in say ten hours
flight time, for a 40 TB/h ~ 11 GB/s (90 Gb/s) throughput,
disregarding the time to write to and read from the media (which
applies equally with a stationwagon or FedEx). If the ticket costs
$500, that's roughly 200 Mb/s per dollar (and remember, we are only
relying on carry-on here). What's more, it is relatively trivially
parallelizable at an approximately linear increase in cost, and can be
scaled according to need at each time. If you can live with the risk
of rough handling, the throughput per dollar approximately quadruples
(700-900 Mb/s/$) given a 20 kg per person maximum checked-in baggage
weight.

It might not be the absolute cheapest approach, but it seems rather
hard to beat in terms of throughput per dollar for bulk data transfer,
especially if you already have someone who would travel anyway and can
be convinced to take a company-approved suitcase in return for having
their ticket paid for.

-- 
Michael Kjörling • https://michael.kjorling.semichael at kjorling.se
                 “People who think they know everything really annoy
                 those of us who know we don’t.” (Bjarne Stroustrup)


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