External hard drives promise almost unlimited storage: For under $100, you can add a terabyte of data to your PC or Mac, portable or desktop. That’s enough for over 750,000 MP3s or photos, or over 230 DVD-sized movies. Every computer out there, from mega-huge towers to compact nettops and netbooks, can connect to at least one hard drive. If you’re lucky enough to have multiple input/output ports, you can hook up many more. Auxiliary storage allows you to back up your system files, in case your primary system goes kaput.
Hard Drive Types
There are two types of external drives. Desktop-style drives, with 3.5-inch mechanisms inside, require a power adapter. Desktop drives are designed to stay in one place, usually on your work surface at home or at the office. If you’re buying a desktop-style drive for active use (video or lots of file transfers), look for one with a built-in fan, as the extra cooling will extend the drive’s life expectancy. Notebook-class (aka pocket) hard drives, like the Apricorn Aegis Padlock Pro $738.99 at Amazon ($759.00 direct, 4.5 stars) and Iomega eGo $139.95 at Adorama ($199.99 list, 4 stars), are usually 2.5-inch or 1.8-inch mechanisms powered through the connector cable without the need for a power adapter. A 2.5-inch pocket drive can fit in a coat pocket and some pants pockets, while 1.8-inch drives can easily fit in your jeans.
Desktop-style drives currently top out at 4 Terabytes (TB) per mechanism, but some drive makers put two to four mechanisms into a drive chassis for more storage (i.e., two 4TB drives equal 8TB of storage). Notebook-style drives come in capacities up to 1.5TB, but capacities from 250GB to 750GB are more common.
A word about multiple drives: you can increase capacity, speed or data protection by buying an external RAID array, but multiple drives add expense and (some) complexity. Once you connect a simple (single volume) external RAID array to your PC or Mac, it will show up and act as any other external drive. After that, it can become more complex. You should consider a drive with support for RAID levels 1, 5, or 10 if you’re storing really important data that you can’t afford to lose. There are other RAID levels for speed, capacity, and other factors like software vs. hardware RAID. Please read Samara Lynn’s excellent primer RAID Levels Explained for more.
External solid-state drives (SSDs) are found mostly in the notebook-style form factor, but these are still relatively rare because they’re pricey in terms of cost per gigabyte. They’re currently limited to smaller capacities, specifically in the 64GB to 512GB range. We recommend that you buy SSDs for use as internal rather than external drives. Besides, unless you’re looking for SSD’s shock-resistance attributes, the drive will be wasted if you use the USB 2.0 interface (rather than, say, eSATA, Thunderbolt, or USB 3.0) to connect the SSD to your system, since the transfer rate USB 2.0 is so much slower than either these three interfaces. eSATA, Thunderbolt, and USB 3.0 external SSD drives are available now, but they are much more expensive than spinning hard drives: for example, a simple 500GB USB 2.0 (spinning) hard drive goes for about $80, A 240GB dual SSD using Thunderbolt is over 10X that at $899.99.
BY:CLC4U ; PC Magazine