The original spec for USB 2.0 is 60MB/s (or 480Mbit/s) raw data rate; that’s the fastest it was designed to transfer data across the wire.
Prior to 2005, USB 2.0 was pretty speedy for most purposes. The spec had already been in existence for well over a few years by this point, and vendors loved it as did consumers. Everyone was happy.
Today in 2011, USB 2.0 isn’t what it used to be. Sure, it’s still as universal as ever and works with everything, but the problem is that the data rate is still mostly the same while data storage is much cheaper and more affordable. In other words, it takes way too long to move our stuff over USB 2.0 because we have so much more stuff.
How cheap is storage today? A 2TB drive is $80 at the time of this writing. That’s $0.04 per GB.
How long does it take to transfer data over USB 2.0?
In practical application, USB 2.0 achieves a maximum bulk data rate of about 40MB/s. You may achieve a better rate depending on your southbridge and if you use an external enclosure with its own controller to assist, but we’ll assume the worst and that you’re only able to achieve the 40MB/s.
Here’s a quick rundown of how long it would potentially take to transfer certain amounts of data. The ones highlighted in red are the times when it would actually bother people to wait that long to get something transferred.
(These figures are rounded and somewhat rough, but they get the point across.)
1.44MB (Floppy disk size)..... Less than a second 700MB (CD disc size)......... Under 20 seconds 1GB (1,024MB).............. Under 30 seconds 2GB (2,048MB).............. Under a minute 4.7GB (DVD-5, 4,813MB)....... 2 minutes 6GB (6,144MB) ............. 2.5 minutes 8GB (8,192MB).............. 3.5 minutes 16GB (16,384MB)............. 7 minutes 32GB (32,768MB)............. 14 minutes 64GB (65,536MB)............. 28 minutes 128GB (131,072MB)............ 55 minutes 256GB (262,144MB)............ 1.8 hours 512GB (524,288MB)............ 3.6 hours 1TB (1,048,576MB).......... 7.3 hours 1.5TB (1,572,864MB).......... 11 hours 2TB (2,097,152MB).......... 14.6 hours
If you’re wondering if there is an external hard drive enclosure with a USB 2.0 interface can in fact support 2TB sizes, the answer is yes – not that I’d recommend going that way, but it is available.
If you’re thinking "My USB 2.0 speeds are WAY slower than that!", it’s because you have other USB devices using the bus. To achieve the best possible rate, use as little USB devices as possible or use a bus that isn’t shared by any other USB devices.
Going with a big external drive? Consider eSATA and/or USB 3.0
External SATA, better known as eSATA, is a good choice to go with if you’re OK with the fact the maximum cable length available is just under 7 feet (6.6′ or 2 meters to be exact), and that you will most likely need an eSATA card for your desktop or laptop, both of which are cheap and widely available.
Standardized in ’04, eSATA is a proven reliable technology with its only real drawback being you probably need the extra hardware noted above to use it for every computer you have.
USB 3.0 is still very new but there are already plenty of new motherboards coming bundled with them, cards are readily available, and as far as enclosures are concerned, oh yes, can do – and they don’t hit the wallet too hard either.
Riding the fence on whether to go with USB 3.0 or eSATA?
This one’s easy to answer – go with USB 3.0.
Why? This is best cited by example.
Chances are the next laptop you buy will have USB 3.0 built right into it, but not eSATA. For whatever new computer you buy, be it laptop, desktop or even new motherboard for a self-built, it will have USB 3.0 ready-to-go, but not eSATA ports unless you very specifically look for them first.
In other words, going with USB 3.0 means less hardware you have to buy in the future. You know USB 3.0 is going to be there, but not eSATA. In addition, USB 3 is backward compatible to 2, so if you run into a computer that doesn’t have 3, you know it will have 2 so you can still connect your external drive.
I’m not saying eSATA is bad because it certainly isn’t – but it does fall short when it comes to how many computers actually have eSATA ports. You want ports that will be available on any computer you use, and for that, USB is the better choice.