Ummm,,,,,
The enclosures either support 2.5" drives (laptop-sized drives) or 3.5" drives (desktop-sized drives).
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Of the desktop 3.5" enclosures, they usually ONLY either take a IDE or a SATA hard-drive, so you need to make sure the enclosure and the hard-drive are the same types. Also--some of the cheaper enclosures have a size limitation; 300Gb is the limit of the cheaper one I have. It might be possible to create and/or access different partitions on the same external hard-drive, but I don't know. Never heard of anyone trying.
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The enclosure-to-PC connections are USB (either 1 or 2) and FireWire.
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Important Note: hard-drives in external enclosures run very hot if used hard. That is--if they are thrashed a lot. It's best to avoid defragging external hard drives, especially if you have a cheaper-brand of drive. Overheating drives will cause data corruption. I've seen at least one external enclosure that had a built-in fan.
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Regarding hot hard-drives (inside the PC case):
Many PC cases with regular HD mounting have a spot in front of the hard-drives for a fan, but it's best to just make sure there's enough holes in the case to get decent air flow where you need it. Many cheaper cases really don't have good air flow, and the best/easiest/cheapest way to fix that is to cut strategic holes.
How hot are your hard drives?
Two free HD temp monitoring programs are-
HDD Thermometer - http://www.rsdsoft.com/hdd-thermometer/index.php (requires free registration)
SpeedFan - http://www.almico.com/speedfan.php
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....I don't know if monitoring programs will read temperatures on the external drive enclosures.
I have two HD's on a controller card (that runs them as SCSI devices) and no HD temperature-monitoring program I ever found could read their temperatures.
For HD's connected normally to the motherboard, it shold all work automatically.
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