That's what my main backup device is, an open enclosure, only they call it a docking station. It is primarily USB3, but USB 2 works also. It does a great job, and my hard drive remains cool.
That 500GB FreeAgentXtreme that I have, has USB 2, Firewire & eSATA ports. I have a BYTECC SuperSpeed USB3 to eSATA 3 Gps adapter that works well with it. This allows for computers with only USB3 ports to use their eSATA components. Here's the link to the product that I bought, and if you read the reviews, you'll see that I reviewed it myself. It's really handy, before I bought my USB3 docking station, it's what I was using, converting my USB3 port to eSATA. Little, if any difference in speed.
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I don't really care for those retail packaged backup drives anymore. They're overpriced, and the drives tend to be the slower ones, and usually of cheap quality. But I'll say this for the FreeAgentXtreme, it's a good retail backup drive. It's a 500GB, 16MB cache & runs at 7200 rpm. If my desktop drive (the OEM 320GB WD Caviar Blue) were to fail, I'd probably crack the casing off that FreeAgent & place it in there. I have plenty of other backup space available to me.
That's why I bought 1TB, 32MB cache, 7200rpm bare drives when Newegg or Amazon ran them on sale for $49.99 to $59.99 each. My only regret was that I didn't buy 2 of those Samsung HD103SJ's from Amazon, rather than 1. I had the money, but as often as HDD's were on sale, I passed up. When I tracked the last one that I ordered, I noticed then that the price had doubled. I ordered it in the nick of time.
If nothing else, I could have sold that drive for enough to mostly pay for the SSD that's on my wish list. They are dropping in price, no way am I'm giving $159 for another of what I have (that's the going price now), when SSD's are becoming less costly by the GB than ever. But I don't want a last generation SSD, the more recent ones are faster. I like the looks of that M4.
Cat