If you’ve been in IT long enough, you’re bound to hear the phrase “never underestimate the bandwidth of a station wagon filled with backup tapes.” This was especially true back in the days of dialup connections and leased lines. How does it scale today? First, we have to decide what kind of media we’re going to use. Tape drives are not nearly as common as they once were and their storage density really isn’t impressive. Instead, lets use the most storage dense media that mere mortals can purchase retail (at the time of this writing): The SanDisk 64GB Ultra MicroSDXC.
Now we have our storage worked out, what are we going to haul it in? These days you can’t really get a good sturdy station wagon, but the modern equivalent seems like it would be the SUV. Since Chevrolet Suburbans have been around for so long, I’m going to pick that. According to Chevrolet.com the 2014 Suburban has 137 cubic feet of cargo space. So, how many MicroSD cards can you fit in there?
First we need to find out how big these little guys are, exactly. Wikipedia says that they are 0.59×0.43×0.039 inches. Now, time to do some math:
First, figure out how many cubic inches a Suburban can hold: 137ft³ = 236736 in³
A MicroSD card is only .01 cubic inches, so if all things were equal you could stuff 100 64gb SD cards into a cubic inch of space! But, that does not seem realistic. In fact it doesn’t even seem remotely possible. Plus, Micro SD cards are oddly shaped. Plus, nothing ever stacks just perfect and we have to put them in boxes of some sort that can support the weight of thousands of cards. So, we’re going to reduce that number by 20% when we’re done.
Given the dimensions of the MicroSD card and the size of a cubic foot, a little math later… 174,646 MicroSD cards per cubic foot. Now trim 20% off and you have 139716 MicroSD cards per cubic foot. Remember, we have 137 cubic feet to fill.
19 Million Micro SD Cards
19,141,092 MicroSD cards will fit in a 2014 Chevy Suburban. What does that come out to in Capacity?
1,225,029,888 GigaBytes (Yes, that’s over 1.2 billion GB’s!)
1/12 Google (per xkcd.com)
398,772 3TB hard drives
Now let’s talk about Bandwidth. We’ll use the old “New York to Los Angeles” as a benchmark. According to Google, that’s a 2,790 mi, 40 hour trek. Since bandwidth is generally measured per second, we’ll measure the trip that way too. A 40 hour trip is 144,000 seconds. Now lets measure the bandwidth:
1,225,029,888 GB in 144,000 seconds = 68057Gbps
In comparison, ATT’s OC-768 fiber optic cable transfers 38.486016 Gbps which is only a 1/1768th of the bandwidth of the Suburban full of MicroSD cards.
That’s a whole lot of bandwidth! One thing we haven’t considered though is actually reading and writing the data off of all those cards, and then putting it back in order. That would take far more time than the actual trip itself, but we’re not counting it because the original saying “Never Underestimate the Bandwidth of a Station Wagon Filled with Backup Tapes” didn’t count it either.
So, when you’re trying to move lots of data, Never Underestimate the Bandwidth of a Suburban Filled with MicroSD cards!