A hard drive is a sealed unit containing spinning magnetic disks with heads that can position themselves anywhere on the disks to read and write data to them. Think of it as a record player that can both play and record music. Most hard drives are internal, buried deep inside desktop and notebook computers. Replacing an internal hard drive is tricky and should be performed only by someone who knows what they’re doing. However, external hard drives are simple enough for anyone to use.
External hard drives are basically the same as the internal hard drives you would find inside of computers housed in an enclosure with a USB, eSATA or FireWire port. The enclosure protects the bare drive and provides power and data ports to it. An external hard drive makes it easy to add more storage space to a computer without having to open it up. It’s like putting a storage shed in your yard when your basement becomes full. External hard drives also make it easy to transfer data from one computer to another.
The first thing to consider in an external hard drive is capacity. External hard drives have capacities typically ranging from 250GB to 2TB, and a lot more if the unit contains more than one drive.
If you’re in need of an external hard drive because your computer’s internal hard drive is full, buy one with at least double that capacity. To make your buying decision easier, consider that the smallest external hard drives available now have capacities of 250GB, followed by 320GB and 500GB drives. And because you can never really have too much space, your best bet is to buy the largest-capacity drive that fits your budget. If you need even more storage space than 500GB drives offer, external hard drives with expanded capacities of 1TB and more can now be acquired.
The disks inside bare hard drives spin at a certain speed, and the faster they spin, the faster data can be written and read. Most hard drives spin at 5,400 rpm and 7,200 rpm, the latter usually outperforming the former. Note that high performance, 10,000 rpm and 15,000 rpm hard drives are used in servers, workstations and other applications in which performance is critical, but you won’t find those rotational speeds in consumer grade external hard drives.
Higher-capacity drives tend to spin at 7,200 rpm simply because they use newer technology, but don’t shy away from something simply because it’s only 5,400 rpm. Sometimes you’ll even see the same basic external hard drive available in both rotational speeds. If you often find yourself copying multiple gigabytes to an external hard drive, the faster spin speed will save you some time. However, if you rarely copy that much data, then it’s better to shop by price and forego speedier performance.
Solid-state hard drives, or SSDs, are not your conventional hard drvie. Instead of spinning disks, SSDs contain flash memory chips and no moving parts. Some SSDs are faster than conventional hard drives, and all are more resistant to shock and vibration, but you pay a lot more per GB of storage space and SSDs don’t offer nearly as much capacity as conventional hard drives do.
Bare hard drives come in two basic sizes: 2.5-inch and 3.5-inch. The 2.5-inch drives are used in portable notebook computers and portable external hard drives, while the 3.5-inch drives are used in desktop computers and desktop external hard drives.
Using 2.5-inch hard drives in portable external drives makes sense because they allow for a smaller, lighter unit that uses less power. Portable hard drives will fit in a shirt pocket, provided your shirts have relatively big pockets. Regardless, portable drives are much smaller than desktop drives, so if you often have to carry one with you, portable external hard drives are the way to go.
Because portable hard drives are often ported from place to place, they run the risk of being dropped from time to time. For that reason, some manufacturers offer portable hard drives with rugged enclosures. These contain the same basic drives as non-rugged units, but they feature shock-absorbing enclosures, usually made of rubber, that protect the drives from the daily bump and grind. But be warned that these will break if you abuse them enough.
Portable hard drives are typically bus powered; meaning that they receive power from their interface cable, so no AC power adapter is needed. This lets you use the drive with a notebook computer when you are nowhere near an AC outlet. It’s also one less thing to pack and carry.
Desktop-size external hard drives contain 3.5-inch drives, making them bigger and heavier than portable units, and they also require an AC power adapter.
There are several types of interfaces, but the type of interface, or port that your computer has will largely determine the type of interface you need on an external hard drive. Most Macs have FireWire, while most PCs don’t. Apple has also introduced the Thunderbolt port and the few external hard drives with this new port are very expensive because of the high data-transfer rate of 20Gbps. But all computers have USB 2.0, and some of the latest ones now have USB 3.0.
USB 2.0 is by far the most common interface found on today’s computers, which is why it’s also the most common interface found on external hard drives. USB 2.0’s maximum throughput is 480 Mb/s, or 60 MB/s, but you’ll typically see only 30-35 MB/s in real-world applications. If your computer has USB 2.0, you can safely invest in a USB 2.0 external hard drive with the assurance that you can connect it to just about any computer in the world.
Basic drives have only a USB 2.0 port.
Some external hard drives now feature a USB 3.0 interface. USB 3.0 is specified at 4.8 Gbps, or 614 MB/s, but you’ll see about 400 MB/s in real-world use. While most computers don’t yet have a USB 3.0 port, USB 3.0 is backward-compatible with USB 2.0. So you can invest in a USB 3.0 hard drive, use it now with a USB 2.0 computer at USB 2.0 speeds, and reap the rewards of faster throughput once you buy a computer with the faster USB 3.0 interface. Some USB 3.0 external hard drives come with a USB 3.0 interface card, and you can always buy a card separately if a drive doesn’t come with one.
This drive has a USB 3.0 interface.
FireWire 400 provides 400 Mb/s, or 50 MB/s throughput, and FireWire 800 doubles the throughput to 800 Mb/s, or 100 MB/s. If you work primarily with Macs, FireWire is the way to go. Some newer computers have eSATA, or external Serial ATA ports, for connecting external peripherals such as hard drives. eSATA is as fast as internal SATA, providing 3 Gbps, or 384 MB/s throughput, or closer to 300 MB/s in use.
Here’s a triple interface with USB 2.0, FireWire 400, and FireWire 800.
Here’s one with eSATA and USB 2.0.
External hard drives with only eSATA interfaces are rare, but many external hard drives have various combinations of ports, including USB 2.0, USB 3.0, FireWire 400, FireWire 800, and eSATA. If you buy a triple- or quadruple-interface hard drive, you can rest assured that it will connect to any computer that’s out there.
The very latest type of interface, called Thunderbolt, was developed by Intel and brought to market by Apple, and now offered in some of the latest MacBook Pro models. Thunderbolt basically combines PCI Express and DisplayPort into a single interface that offers data transfer rates up to 10Gbps. For anyone lucky enough to have a computer with a Thunderbolt port, a handful of external hard drives featuring Thunderbolt ports are available.
If you have an old computer that you’ll never use again but its hard drive is still good, or if you upgrade the hard drive in your desktop or notebook computer and don’t know what to do with the old drive, you can always install it in an enclosure that will convert it for external use.
You have to know whether the drive is a 2.5-inch or 3.5-inch unit, and whether it’s Parallel ATA (PATA) or Serial ATA (SATA). If it came out of a notebook computer it’s a 2.5-inch drive and if it came out of a desktop computer it’s probably a 3.5-inch drive. If its connector looks like the one below on the left it’s PATA and if it looks like the one on the right it’s SATA.
B&H carries a wide variety of hard drive enclosures for 2.5-inch and 3.5-inch drives. Most of them are for SATA drives only, but some will accept SATA or PATA. The only other decision you have to make is what kind of interface you need on the drive enclosure. As mentioned before, USB is nearly universal and very common on PCs. FireWire is more common on Macs.
If you’re into multimedia, there’s a special kind of external hard drive that will surely appeal to you. Multimedia hard drives are typically used to store video and play back the video on an HDTV set. They feature component and HDMI video outputs and come with a remote control, so that you can enjoy your entire digital multimedia collection on the big screen.
If you keep top-secret or personal files on your external hard drive and there’s a chance you could lose it or that it might get stolen, you will want a unit with password protection and data encryption. Encrypting your data prevents unauthorized users from accessing it. In other words, if someone doesn’t have the right password, they can’t get at the data. Some drives use biometric authentication to protect the data. With this configuration, your fingerprint is used for access instead of a password.
When a hard drive fails, you usually lose all the data stored on it. While most external hard drives contain just a single drive, some contain two or more drives and use RAID technology to increase performance and capacity or to provide data redundancy.
Most of the external hard drives that feature RAID technology support RAID 0 and RAID 1. RAID 0 splits data evenly across two or more disks to increase performance or to create a single virtual drive from multiple smaller drives. Basically, this gives you one drive letter instead of many. RAID 1 creates an exact copy, or mirror, of a set of data on two or more disks so that if one drive fails, the data can be recovered from the healthy drive(s). Note that duplicating all of your data on two separate external hard drives will give you the same peace of mind.
Most external hard drives come with some sort of automatic backup software that makes backing up your data a little easier. You can usually set the software to back up your computer on specific days and times. Just keep in mind that you have to leave your computer turned on for the times when you have backups scheduled.