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If you don't know what eSATA is, you don't need it. USB 3.0 is plenty fast. If your computer has a USB 3.0 port you'll be able to transfer 10-15 GB in under a minute for practical circumstances, and possibly 20-30 seconds under best conditions. The spec is for 5 gigabits/second.
5 x 1024 = 5120 Mbits/sec ÷ 8 = 640 MBytes/sec ... so, 6,400 MB/s = 6.25 gigabytes every ten seconds. Some differences depending on if you are writing to the drive or reading from it, and transferring large single files is far more efficient than thousands of very small files.
NOTE: you will need a SATA III (6.0 Gbit/sec) drive to make use of your USB 3.0 maximum potential. A SATA II (3.0 Gbit/sec) drive will not perform at the top USB 3.0 performance levels.
Compare to USB 2.0 which is 480 Mbits/sec (60 MB/s), and it's rare and difficult to come very close to that maximum. Practically, when I write a 10-12 GB directory of 15 or 24 video files to my external USB 2 drive it takes about 15-18 minutes. So, if you do that about twice per day, it's really fast enough. And, USB 2 is more than a dozen times fast enough to play music and video files direct from the external storage to the computer. Effectively that's a Read operation, which is faster by about 20%-30% than a Write operation.
What will screw you a bit is if you need to do a 1/2 or full terabyte transfer. Under USB 2.0, start the transfer, go to bed and it's usually done when you wake up. Under USB 3.0 you can go get a cup of coffee and it'll be done by the time you drink about half of it. So, decide how often you will make transfers in those size ranges, and try to estimate for the next three to five years that you'll have the drive.
Next, your real factor is budget. Hard drives got pretty expensive last fall when most of the industry manufacturing got wiped out by flooding in Thailand. Prices should have dropped around Christmas when most of that got fixed, but some interesting things happened in the industry because of that event. There has been quite some consolidation, so competition dropped. The result is that prices are still stupid high ... for no other reason than price gouging.
» Technology » WD HDD Industry Will Be Supply Constrained Due to Thailand FloodingIt has become better a little, but here's an example:
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SAMSUNG EcoGreen F4 HD204UI 2TB 32MB Cache SATA 3.0 Gb/sThe standard price was about $80 last August. Then it went up to about $180 last September. Now they're "only" $120. Unfortunately, today is the last day for a $20 discount, where it would "only" be $100. But, last summer I bought two for $70 each, and even picked one up for $60. This is an example of a drive that will not perform to top USB 3.0 specification ... but it will still be pretty bloody fast compared to USB 2.0.
Samsung isn't even owned by Samsung anymore ... it's now a division of Seagate. And Seagate was THE worst hard drive manufacturer for the two to three years prior to last August. They've become better ... but their reliability and quality control still scare the crap out of me.
All this is the long way of saying that your chances of getting 4 TB storage for under $200 are pretty close to zero at this time.
I still recommend this external enclosure:
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Rosewill R2-JBOD Aluminum 3.5" USB 2.0 DUAL-BAYWatch for it on sale and you can get it as low as $30 or $35. However, it is USB 2.0 ... they never started making it in USB 3.0. A real shame. You can run it with only one hard drive in it and then get a second one later to pace your budget. From the description, it doesn't take drives larger than 2 TB, which could be a con if you're looking at 3 TB drives, for example.
It comes with two essential features, in my mind: it has an internal fan (which can be turned on and off separately) and it has it's own power switch .. which gives me great comfort when trying to isolate my storage drive from unanticipated power on/off events. Further, the thing is built strong enough to park a car on out of solid aluminum, which only helps to act as a heat sink and dissipate heat.
So, that's a large storage brick. It's slow, but about as low a price as you'll get away with for the amount of storage. You can look at other dual-drive enclosures, but they're more expensive and not really any better ... unless you can find one with USB 3.0, and/or support 3 & 4 TB drives for future use. You could put one 2 TB drive in it immediately and spend about $150-$160 right now. Shop around and maybe you could do that for ~$130. A second 2 TB drive will run you $100 to $140 (depending on the model you select) ... so a full 4 TB solution looks like about $250 right now.
An alternate:
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Rosewill RX-358 U3C SLV Aluminum / Plastic 3.5" Silver USB 3.0 & eSATAI have a slightly older model of this one that has only USB 3.0 and not an eSATA (which I don't need anyway). Picked it up for $20 on sale. Love it. I haven't used it on a USB 3.0 port yet, but it performs at the bleeding edge of the USB 2.0 specification. It's also supposed to support 3 TB drives ... so you could consider it as a single-drive external, well-cooled solution. I run a 750 MB Western Digital Caviar Black SATA 6.0 Gb/s out of it and it is SOLID. The 750 MB drives are off the market now, but here is the slightly larger equivalent:
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Western Digital Caviar Black WD1002FAEX 1TB 7200 RPM 64MB Cache SATA 6.0Gb/sIn my previous post I suggested the following:
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Seagate Momentus XT ST750LX003 750GB 7200 RPM 2.5" SATA 6.0Gb/s HybridCurrently ~$155, but I've seen them go for ~$135 - $140 on sale. This is a hell of a performance drive. Look to this if you REALLY feel the need for speed.
You will want a USB 3.0 enclosure for it, otherwise you're throwing your money away.
If you still want the small form factor + portability of a 2.5" external but the bleeding edge speed of the Momentus is more than you require, look to something like a Western Digital Scorpio Black:
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Western Digital Scorpio Black WD7500BPKT 750GB 7200 RPM 16MB Cache 2.5" SATA 3.0Gb/sA couple things here. The Black edition is preferable to the Blue edition. Not for performance, but for reliability. The same goes for the 3.5" Caviar drives. There is also a 1 TB version, but watch carefully for the exact dimensions ... the 1 TB drives fit into laptops, but are sometimes too thick to fit into an external case. Definitely pay attention to that detail.
Final thought: the forum link in my previous post about battery back-ups & surge protection. Read it if you wish to understand why that's an important factor. The electricity coming out of your wall has a lot of fluctuation in it and can play hell on sensitive electronics. Hard drives, especially magnetic, mechanical ones, are just about as sensitive as they get. If you care for your data, look at quality surge & battery protection.
There was some more discussion here:
» Technology » Just lost another HD. are docking stations to blame?Also, that topic gives an idea of why I do not trust docking stations, very especially cheap ones. They are cheap for a reason: they are missing essential, quality electronics that protect your hard drive.
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EDIT: added some stuff & fixed some typos ]