In the tail end of this article I briefly touched upon that if you want to use a big external hard drive, USB 3.0 or eSATA would be the best choice because both run circles around USB 2.0 and both technologies are affordable to anyone who wants them.
With either technology, both have their pros and cons, so I’ll cover a few of them.
eSATA has more tenure than USB 3.0 does since it’s been standardized since 2004. As such, all modern computers recognize it, usually without the need for additional drivers.
The same cannot be said for USB 3.0 presently. For example, on the motherboard I have which is well under 6 months old, I did have to use the motherboard driver disc in Windows 7 just to get Windows to recognize the on-board USB 3.0 ports.
If going with USB 3.0 on a self-built PC, it’s more or less guaranteed at this point you will have to install drivers.
USB 3.0 has only one version, 3.0. USB has a longstanding history of sticking to a version number for the long haul; this is good because it involves a lot less guesswork on whether something you plug into it is compatible or not.
SATA can get real confusing real quick because nobody can seem to decide on what to call the revisions. However the three official revisions are SATA Revision 1 (1.5Gbit/s), SATA Revision 2 (3GBit/s) and SATA Revision 3 (6GB/s). "SATA I", "SATA II", "SATA III", "SATA 300" and otherwise at this point don’t count. That’s the industry saying that – not I.
The Big Question concerning the SATA revisions is does it matter concerning eSATA? Not really. It is highly unlikely you will notice any difference between SATA Revision 1, 2 or 3 when connected via eSATA cable. When directly connected to the motherboard, that’s a totally different story, but with over-the-wire eSATA, you’re not going to experience any significant improvement in transfer speeds between the revisions because of the wire limitations.
Full Supported vs. Mostly Supported
eSATA is fully supported across the board and there is no guesswork involved with it, thanks to its tenure in the market.
USB 3.0 is either going to be fully supported or ‘mostly’ depending on the hardware you have. For example, some motherboards are being delivered with USB 3.0 ports that do not have the capability of 3.0’s fastest transfer rate. It is faster than USB 2.0, but at the time of manufacture was not made to completely support 3.0’s top speed.
The fix for this is an easy one – use a card. If you notice your USB 3.0 isn’t transferring at what it’s supposed to be, a fully-supported card will cure that ill.
It’s important to note that this more or less only happens on motherboards and not card peripherals. As for why, I have no idea, but that’s the way it fared out.
By mid-2011 all motherboards should support USB 3.0’s fastest transfer speeds 100%.
Additional note: A motherboard with USB 3.0 ports that do not deliver the fastest transfer speeds doesn’t mean 3.0 won’t work. It will work, but just not at full capability.
USB 3.0 acts just like 2.0 did. Ports are in the back or brought to the front via hub or 3.0-capable additional USB ports on your computer case. It can also be included in a card reader.
eSATA is installed and used either by card peripheral or all-in-one card reader. This may annoy some people because ports in the back are annoying to deal with. If you want one in the front, you have to install a large optical-drive-sized all-in-one card reader just to get it, which may be equally annoying – especially considering there’s never been a card reader made that doesn’t look like it came straight out of a 1979 Radio Shack Catalog (i.e. they’re ugly).
This is the information people want to know more than anything else when it comes to USB 3.0 vs. eSATA.
Unfortunately there is no direct answer. I can’t say "eSATA transfers at X rate all the time", nor can I say that for USB 3.0. All I can give are ranges.
This can be as slow as 35MB/s to as fast as 150MB/s. The range varies wildly because it depends what you’re connecting your eSATA drive to. If you connect your eSATA external drive via a laptop Cardbus or ExpressCard adapter, it will be on the slower side. On a regular desktop PC you’ll get much faster transfer rates.
There really isn’t enough data out there concerning the practical data rate of USB 3.0. It has been speculated that with included protocol overhead factored in, it is possible to achieve 400MB/s. And yes that’s darned fast. 2TB can be transferred in less than 2 hours easily at that data rate. But then again it was speculated that USB 2.0 could achieve 60MB/s easily, and nobody achieves that (we get 40MB/s at best).
As a plain flat-out guess, I would say USB 3.0 will probably achieve 225 to 300MB/s on average. Maybe. Don’t take that as gospel.
It is well known that USB 3.0 will easily outrun eSATA in its current form, because SATA Revision 3’s speeds can only be achieved direct-from-motherboard. If going external on-the-wire with eSATA, you’re not going to get over 150MB/s even if all your stuff is SATA Revision 3 equipped.
USB 3.0 is the better of the two
I don’t pick USB 3.0 for speed but rather for convenience. It’s backward compatible to USB 2.0 and every modern computer has USB ports, so you’re never stuck without a port to plug into. eSATA can only go where there’s a port, and that means you’ll have to buy a card peripheral for every computer you want to connect it to.