

The bandwidth of a fully laden 747 - jgrahamc
http://blog.jgc.org/2010/07/bandwidth-of-fully-laden-747.html

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evgen
While shipping tapes fits the original metaphor (station wagon full of mag
tape was what we were told to never underestimate back in the 80s) a more
practical example would be to use 2T hard disks. You would lose out a bit on
information density, but the drives could be slammed straight into a storage
array without the transfer step that tape requires.

A 2T disk is about 400cc of volume and 660g in weight. A 747-8 freighter has
close to 690 m^3 of cargo space. Round that down to 680 and we could put 1.7
million disks into a 747-8 by volume. Unfortunately they would weigh more than
one million kilos. By weight it could hold around 212,000 disk drives
containing 424 PB. This gets you close to the same numbers that jgc came up
with, but in a more useful format for attaching directly to a storage array.

~~~
tomjen3
You could do the same with SD cards, the card readers for that are very, very
cheap and you could fit a lot more data into it.

~~~
evgen
True, but I was trying to keep this in the realm of reality. A large org could
actually shift this much data in a single day from step A (shutdown/pull
drives) to Z (start using the new cluster on the other side of the world)
using this method. Expecting someone to have a million or more SD card readers
is not really a practical plan. I could have probably also increased the
density by using blue-ray data disks, but having a similar number of optical
drives waiting for disks was also not really practical.

At one time this general process was how chunks of yahoomail migrated from our
original Four11 colo on stanford campus to the yahoo colos in san jose and
sunnyvale (except it was netapp drives and shelves packed into my miata
instead of a 747 -- 1T of 18G drives with the top down doing 80-90 southbound
on 101...fun times :)

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tome
It's going to take a lot more time than 10 hours to get 427 PB onto those 2.8m
cartridges, and then get the cartridges onto the 747.

~~~
sfall
assuming you use DAT 320 tapes and use 3 Gb/sec,
[http://h10010.www1.hp.com/wwpc/us/en/sm/WF06a/12169-304612-3...](http://h10010.www1.hp.com/wwpc/us/en/sm/WF06a/12169-304612-3446234-3446234-3446234-63890.html)

It would take about 55 min to load each tape and another 55 min to unload.
Being there are 2.8 million tapes it would take 2,566,667 hours to load, and
the same to unload.

((427 petabytes) / 5 million) / 60 = 1.49247317 gigabytes per sec

~~~
shalmanese
Except you can parralelize the workload significantly.

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shabble
A more thorough (and dare I say entertaining) version involving SD cards in a
station wagon: <http://dansdata.com/gz105.htm>

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mansr
32GB microSD cards (the largest currently available) at ~0.5g each have a much
higher data density.

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narkee
In South Africa, pigeons are "faster than broadband":
<http://news.bbc.co.uk/2/hi/8248056.stm>

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rbanffy
What do you mean? An African or European 747?

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amalcon
It would be more interesting to compare the cost along with the total
bandwidth. It's very expensive to fuel a 747 for a trans-Atlantic flight, but
the information density should be high enough to make the cost comparison
interesting.

~~~
bd
Very rough estimate based on passenger ticket prices gives about $20 per GB/s.

    
    
      SF <-> London is about $1,200 for return ticket (Kayak)
      747 can have about 400 passengers
      bandwidth is 12 TB/s (from the post)
    
      400*1200/2 = $240,000 cost of flight
      $240K / 12,000 GB/s = $20 per GB/s
    

This should be an upper bound. I assume flying cargo (bought in bulk) would be
significantly cheaper than flying people with individually bought tickets.

~~~
amalcon
$20/GB/s for ten hours. If you want to compare to bandwidth prices, it has to
be scaled up to a month:

    
    
      24*30/10 = 72 flights/month
      $1440 per month per GB/s
    

Like, you, I suspect it would be significantly cheaper than this, but that
calculation would require data I don't have.

~~~
bd
Ah, yes.

For the lower bound, we can estimate just the price of fuel (no plane
amortization, crew and ground personnel costs, airport taxes, etc).

This seems to be currently about $54K per flight (London to San Francisco).

    
    
      747 burns about 5 gallons per mile
      LHR to SFO is 5,367 miles
      current jet fuel price is 201.1 cts/gallon
    
      5367*5*2 = $53,670
    

So monthly price per GB/s should be somewhere between $322 - $1,440.

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Vivtek
I upvoted this _only_ because of its delightful title. I don't even need to
read the article - the title alone has made my day brighter.

~~~
jgrahamc
Well, I made someone smile. Did you ever read my article "Tonight, I'm going
to write myself an Aston Martin"?

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sh1mmer
Last year Carlos (aristus) and I launched <http://www.cloud-peering.com/> and
spoke at a few conferences to highlight exactly this issue.

Essentially the biggest interop problem in the cloud is the lack o backhaul
sharing. It's the only thing we can't code our way out of.

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joe_the_user
Just to play devil's advocate.

There's unit's miss-match here. The information transfer rate that would apply
to physically moving a storage device would be bits per second per meter
(information-unit/time-unit/distance-unit). Bandwidth is normally measured
with bits and seconds, with no distance unit. The two aren't directly
comparable. If you somehow you had a 20 Kbs rate to Pluto, it would be a
comparable information/time/distance transfer to a fully laden 747.

~~~
jerf
All that means is you need to add a distance conversion factor in, and it all
works fine, albeit tied to that distance. And, lo: "Now assume it flies from
San Francisco to London in 10 hours." The two may not be directly comparable,
but that's ok, because they weren't directly compared. Defining the bandwidth
of that specific flight is perfectly reasonable and no "devil's advocate" is
needed.

(And if you want to point out that this isn't a practically useful number...
well, yeah. But it's perfectly well-defined and unit-correct.)

