Storage buying guide

Looking for new storage devices and need some tips? You're in the right place.

What to look for when buying a storage device

The computing world runs on information, and handling it is crucial. So it's important that you select the best storage device to not only hold your data, but also distribute it. In this guide, I'll explain the basics of storage and list the features that you should consider when shopping. If you're ready to leave for the store right now, though, I've also listed my top picks.

Hard-core users hoping to get the most out of a home storage system should consider a network-attached storage (NAS) server such as a five- or four-bay NAS server from Synology, QNAP, Asus, Netgear, WD or Seagate. Alternatively, if you want to make your new computer run at its top speed, a solid-state drive (SSD) such as the Samsung 850 Pro will make that happen. But if you older machine and don't want to spend too much, upgrading its hard drive to a more affordable SSD, such as the Samsung SSD 850 Evo or the OCZ Trion, will also bring about great satisfaction. For more options on SSDs, check out this list.

If you just want to casually extend your laptop's storage space or find a quick way to back up your data, a nice and affordable portable drive, such as the WD My Passport Ultra, or the Seagate Backup Plus Slim will do the trick. Again, more excellent storage portable drives can be found on this list.

Now if you want to know more about storage, I invite you to read on. On the whole, there are three main points you should consider when making your list: performance, capacity and data safety. I'll explain them briefly here. And after you're finished, check out this related post for an even deeper dive into the world of storage.

Using an SSD like one of these will greatly improve your computer's performance.
Using an SSD like one of these will greatly improve your computer's performance. Dong Ngo/CNET


Storage performance refers to the speed at which data transfers within a device or from one device to another. Currently, the speed of a single consumer-grade internal drive is defined by the Serial ATA interface standard, which determines how fast internal drives connect to a host (such as a personal computer or a server), or to one another. There are three generations of SATA, with the latest, SATA 3, capping at 6Gbps (about 770MBps). The earlier SATA 1 and SATA 2 standards cap data speeds at 1.5Gbps and 3Gbps, respectively.

So what do those data speeds mean in the real world? Well, consider that at top speed, a SATA 3 drive can transfer a CD's worth of data (about 700MB) in less than a second. The actual speed of a hard drive may be slower because of mechanical limitations and overheads, but you get the idea of what's possible. A hard drive's real-world speed tends to be around one-tenth of the SATA3 standard. Solid-state drives, on the other hand, offer speeds much closer to the ceiling speed of SATA3. Most existing internal drives and host devices (such as computers) now support SATA 3, and are backward-compatible with previous revisions of SATA.

Since internal drives are used in most other types of storage devices, including external drives and network storage, the SATA standard is the common denominator of storage performance. In other words, a single-volume storage device -- one that has only one internal drive on the inside -- can be as fast as 6Gbps at most. In multiple-volume setups, there are techniques that aggregate the speed of each individual drive into a faster combined data speed, but I'll discuss that in more detail in the RAID section below.


Capacity is the amount of data that a storage device can handle. Generally, we measure the total capacity of a drive or a storage system in gigabytes. On average, 1GB can hold about 500 iPhone photos, or about 200 iTunes digital songs.

Currently, the highest-capacity 3.5-inch (desktop) internal hard drive can hold up to 6 terabytes, or roughly 6,000GB. On laptops, the top hard drives as well as SSDs can offer up to 2TB.

While a single-volume storage device's capacity will max out at some point, there are techniques that make it possible to combine several drives to offer dozens of terabytes, and even more. I'll discuss that in more detail in the RAID section below.

A layer of protection, like the one this LaCie Rugged drive has, helps keep the internal drive from being damaged by shocks and drops.

A layer of protection, like this LaCie Rugged drive has, helps keep the internal drive from being damaged by shocks and drops.

Dong Ngo/CNET

Data safety

The safety of data depends on the durability of the drive it's stored on. And for single drives, you also have to consider both the drive's quality and how you'll use it.

Generally, hard drives are more susceptible to shocks, vibration, heat and moisture than SSDs. For a desktop computer, durability isn't a big issue since you won't move your computer very often. For a laptop, however, I'd recommend an SSD or a hard drive that's designed to withstand shocks and sudden movement.

For portable drives, you can opt for a product that comes with layers of physical protection, such as the LaCie Rugged Thunderbolt, or the G-Tech G-Drive ev ATC. These drives are generally great for people working in rough environments.

But even when you've chosen the optimal drive for your needs, don't forget to use backup, redundancy or both. Even the best drive is not designed to last forever, and there's no guarantee against failure, loss or theft.

The easiest way to back up your drive is to regularly put copies of data on multiple storage devices. Most external drives come with automatic backup or sync software for Windows included. Mac users, on the other hand, can take advantage of Apple's Time Machine feature. Note that all external drives work with both Windows and Macs, as long as they are formatted in the right file system: NTFS for Windows or HFS+ for Macs. The reformatting takes just a few seconds. For people who are on a budget or want to quickly find the best portable storage system, here's our list of top portable drives.

Yet, this process isn't foolproof. Besides taking time, backing up your drive can leave small windows in which data may be lost. That's why for professional and real-time data protection you should consider redundancy.


The most common approach to data redundancy is RAID, which stands for "redundant array of independent disks." RAID requires that you use two internal drives or more, and depending on the setup, a RAID configuration can offer faster speeds, more storage space or both. Just note that standard RAIDs generally require drives of the same capacity. Here are the three most common RAID setups.

Also called mirroring, RAID 1 requires at least two internal drives. In this setup, data writes identically to both drives simultaneously, resulting in a mirrored set. What's more, a RAID 1 setup continues to operate safely even if only one drive is functioning (thus allowing you to replace a failed drive on the fly). The drawback of RAID 1 is that no matter how many drives you use, you get the capacity of only one. RAID 1 also suffers from slower writing speeds.

Like RAID 1, RAID 0 requires at least two internal drives. Unlike RAID 1, however, RAID 0 combines the capacity of the drives into a single volume while delivering maximum bandwidth. The only catch is that if one drive dies, you lose information on all devices. So while more drives in a RAID 0 setup means higher bandwidth and capacity, there's also a greater risk of data loss. Generally, RAID 0 is used mostly for dual-drive storage setups. And should you choose RAID 0, backup is a must. RAID 0 is the only RAID setup that doesn't provide data protection.

For a storage device that uses four internal drives, you can use a RAID 10 setup, which is the combination of RAID 1 and RAID 0, for both performance and data safety.

This setup requires at least three internal drives, but it distributes data on all drives. Though a single-drive failure won't result in the loss of any data, performance will suffer until you replace the broken device. Still, because it balances storage space (you lose the capacity of only one drive in the RAID), performance and data safety, RAID 5 is the preferred setup.

Most RAID-capable storage devices come with the RAID setup preconfigured, so you don't need to configure that yourself.

Now that you've learned how to balance performance, capacity and data safety, let's consider the three main types of storage devices: internal drives, external drives and network-attached storage (NAS) servers.

Typical 2.5-inch (laptop) and 3.5-inch (desktop) SATA internal hard drives.
Typical 2.5-inch (laptop) and 3.5-inch (desktop) SATA internal hard drives. Dong Ngo/CNET

Internal drives

Though they share the same SATA interface, the performance of internal drives can vary sharply. Generally, hard drives are much slower than SSDs, but SSDs are much more expensive than hard drives, gigabyte to gigabyte.

That said, if you're looking to upgrade your system's main drive -- the one that hosts the operating system -- it's best to get an SSD. You can get an SSD with a capacity of 256GB or less (currently costing around $200 or less), which is enough for a host drive. You can always add more storage via an external drive, or in the case of a desktop, another regular secondary hard drive.

Though not all SSDs offer the same performance, the differences are minimal. To make it easier for you to choose, here's our list of the current best internal drives.

External drives

External storage devices are basically one or more internal drives put together inside an enclosure and connected to a computer using a peripheral connection.

There are four main peripheral connection types: USB, Thunderbolt, FireWire, and eSATA. Most, if not all, new external drives now use just USB 3.0 or Thunderbolt or both. There are good reasons why.

USB 3.0 offers a cap speed of 5Gbps and is backward-compatible with USB 2.0. Thunderbolt caps at 10Gbps (or 20Gbps with Thunderbolt 2.0), and you can daisy-chain up to six Thunderbolt drives together without degrading the bandwidth. Thunderbolt also makes RAID possible when you connect multiple single-volume drives of the same capacity. Note that more computers support USB 3.0 than Thunderbolt, especially among Windows computers. All existing computers support USB 2.0, which also works with USB 3.0 drives (though at USB 2.0 data speeds).

Generally, speed is not the most important factor for non-Thunderbolt external drives. That may seem counterintuitive, but the reason is that the USB 3.0 connectivity standard, which is the fastest among all non-Thunderbolt standards, is slower than the speed of SATA 3 internal drives.

Capacity, however, is a bigger issue. USB external drives are the most affordable external storage devices on the market and they come with a wide range of capacities to fit your budget. Make sure to get a drive that offers at least the same capacity as your computer. Check out our list of best external drives for more information.

Note that there's no difference in terms of performance between bus-powered (a data cable is also used to draw power) and non-bus-powered (a separate power adapter is required) external drives. Generally only single-volume external drives that are based on a laptop 2.5-inch internal drive can be bus-powered, and for now drives like this offer 2TB of storage space at most. Non-bus-powered external storage devices mostly use 3.5-inch internal drives and can combine multiple internal drives, so they can offer more storage space.

Currently, Thunderbolt storage devices are more popular for Macs and, unlike other external drives, deliver very fast performance. They are significantly more expensive than USB 3.0 drives, with prices fluctuating a great deal depending on the number of internal drives you use. Here's our list of the top Thunderbolt drives on the market.

The five-bay Synology DiskStation DS1513+ is one of the best NAS servers on the market.

Synology DiskStations are of the best NAS servers on the market.

Dong Ngo/CNET

Network-attached storage (NAS) devices

A NAS device (aka NAS server) is very similar to an external drive. But instead of connecting to a computer directly, it connects to a network via a network cable (or Wi-Fi) and offers storage space to the entire network at the same time.

As you might imagine, NAS servers are ideal for sharing a large amount of data between computers. Besides storage, NAS servers offer many more features, for example being capable of streaming digital content to network players, downloading files, backing up files from a network computer, sharing data over the Internet, and much more.

If you're in the market for a NAS server, note that its data rate is capped at that of a Gigabit Ethernet network connection, which is about 130MBps at most -- far less than the speed of the internal drives themselves. That said, you should focus on the capacities of the internal drives used. Also, it's a good idea to get hard drives that use less energy and are designed to work 24-7 since NAS servers are generally left on all the time. See this list of the best NAS servers to see my top choices.

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