The high-capacity external hard drives covered in this report are primarily intended for backup. They can also provide long-term external storage for multimedia files, such as digital video, high-resolution photos or music collections that occupy considerable hard-drive space on a computer. Although you'll sacrifice performance with most external hard drives, they can provide a convenient way to increase your storage space with the added benefit that the drive may be unplugged and connected to another computer.
We found the most comprehensive and thorough review sources to be TomsHardware.com and England's RegHardware.com. Both are prolific reviewers of external hard drives, but each has different strengths: RegHardware.com publishes objective single-drive reviews, and TomsHardware.com compares related products in roundup reviews and shows the most comparisons in benchmark tests. Tests at Macworld and CNET are less detailed but still thorough, and they cover most of the newest and most popular drives.
Major computer magazines such as Laptop Magazine, PC World and PCMag.com regularly rate the best external hard drives, but ConsumerReports.org hasn't tested any in the last couple of years. Owner reviews reveal how external hard drives work in backup after backup, month after month. Amazon.com sells hundreds of hard drives and attracts hundreds of reviews, but owners who buy at Newegg.com are sometimes more knowledgeable because this site caters to computer enthusiasts and hobbyists.
External hard drives have tons of storage capacity and modest per-gigabyte (GB) costs. Other external storage options include USB flash drives, which are faster and the most portable, but capacity is currently capped at 256 GB. Furthermore, the cost per gigabyte is higher (significantly so for the largest 256 GB drives) and security is lower. See our companion report on USB flash drives if one or several flash drives will be enough for your storage needs.
High-capacity solid state drives, which are faster than traditional hard drives, are much more expensive per gigabyte than traditional drives and are still relatively uncommon on the external hard drive market. Customers' perception that they are more reliable than traditional drives may not be the case; an August 2011 survey by Kroll Ontrack, a data recovery service, suggested that more than half of solid-state drive users had lost data.
Measured data transfer speed is almost always the major factor in reviewer ratings. It is a big deal if you will actively use the drive, but it might not matter at all if the drive is just for backups. Reviewers also consider methods of connectivity (USB 2.0 or USB 3.0, FireWire, eSATA), ease of use, bundled or pre-installed software, and physical design features, such as whether the drive sits vertically or horizontally (or can be used in either position).
Noise can be a factor as well. According to reviews, some hard drives are quiet in operation, but others generate noise that can be as annoying as a commercial jingle you can't clear from your head.
Reviewers say that backup software makes a difference in the utility of these drives. Nearly all moderately priced to expensive external hard drives come with software to help schedule backups and move files, and features include system rollback capability as well as security options that keep your drive safe from sudden disconnects, shutdowns and virus invasions (a risk for drives that are switched among multiple computers). You don't need to use the manufacturer-supplied software with an external hard drive. You can drag and drop files, bypassing software entirely, or use third-party software. Budget hard drives rarely include backup software, but they are also rarely reviewed.
For the most part, the reviews we found say that the majority of external hard drives do exactly what they are supposed to do. Professional reviews are almost uniformly good across the board. However, user reviews occasionally tell another story. Newegg.com, Amazon.com and CNET's user reviews all have entries from frustrated owners who recount their hard-drive disasters.
Heat and reliability are closely related, and any electronic product that runs too hot can be a failure waiting to happen. Several factors can be used to gauge reliability; those include brand history and reputation, user reviews, and the manufacturer's limited warranty for a specific drive. The manufacturer's mean time between failures (MTBF) specification is not published by all manufacturers, and studies have found that those that do, are not above exaggerating their numbers. The bottom line is that even with an external hard drive, experts still recommend redundant backups of key data. See the What to Look For tab for additional information on how to select the best external hard drive for your needs.