Solid State Drives, Everything You Need To Know

The market is suddenly awash in solid-state drives thanks to the growing abundance and greater reliability of flash memory. Here’s what you need to know about today’s SSD storage.

Solid-state drives are new to the PC storage front, and they’re making waves by offering blistering speeds and greater reliability than traditional hard disk drives. For that, you can thank the NAND flash memory chips that make up every solid-state device.

If you’re not familiar with NAND memory, you need only look at your keychain. NAND is the technology that powers the storage on your USB thumb drive… and your mobile devices and the memory card in your digital camera. Whereas your tiny flash card might use but a single NAND chip, SSDs use multiple chips to achieve their higher capacities.

Storage that uses flash memory is quite unlike the hard disk drives used to hold your computer’s data. The latter rely on speedy actuators to read and write information on spinning magnetic platters. SSDs use electrical charges to read and write the state of individual flash memory cells. An SSD’s flash memory is nonvolatile: Unlike your computer’s RAM, an SSD drive retains your data when you switch the power off. And since the handshake is electric, SSDs can access that data in a fraction of the time it takes a mechanical hard drive to do so.

Sounds ideal, right? Actually, the performance potential of SSDs needs to be weighed against some significant drawbacks. We’re going to outline the pros and cons of the technology and how it compares to traditional hard disk storage. We’re also going to put seven leading solid state drives to the test and let the benchmark numbers do the talking. At this stage in the storage race, an SSD is a big investment; we want to help you maximize your return.

Breaking It Down

Before you make the move from a hard disk drive to a solid-state solution you need to be aware of what you’ll gain and what you’ll give up

The Pros

An SSD’s biggest boon is its performance potential. Unlike hard drives, SSDs don’t have to wait for a physical arm to move read and write heads to specific points on a spinning magnetic platter. Reading from flash memory is a virtually instantaneous process, giving SSDs the ability to reach faster random read times and greater read throughput than magnetic hard drives.

Another advantage to SSDs is their relatively long life span. The NAND flash memory cells found in SSDs can last for years beyond the three- to five-year life expectancy of a magnetic hard drive. Because hard drives include numerous moving parts, they are vulnerable to wear and tear over time, especially if dropped or jostled.

An SSD can still break if you drop it, but as a whole, the lack of moving parts makes the category less prone to damage. If left unbothered, a solid-state drive can last up to 60 years longer than a hard drive in a similar desktop environment. And as an added bonus, SSDs don’t produce any noise and generate very little heat.

The Cons

NAND flash is still a relatively expensive technology, limiting the capacities of solid-state drives and making for a high cost per gigabyte. Some manufacturers have managed to lower the cost of SSDs by using multi-level cell (MLC) technology to cram more bits of data onto a single memory cell. The problem is, MLC tech incurs a performance hit over single-layer cell (SLC) technology. The voltage complexities involved in maintaining the multi-bit cells can significantly slow the speed of write operations.

Unless a manufacturer specifies what kind of flash memory powers its drives, you won’t know whether you’re getting high-performance SLC or low-performance MLC flash. The price tag is the only distinguishing factor outside of benchmarks: MLC drives are among the cheapest SSD drives available (typically half the price of SLC SSDs).

Manufacturers claim SSDs offer better power savings than magnetic storage, but that’s not always true. This greatly depends on the construction of the drive: PATA- or SATA-based SSD drives tend to draw more power than typical hard drives.

Finally, SSDs can suffer from inferior random write and sequential write times because the data on an SSD is stored in kilobyte-size blocks. Adding more data to a block is a time-consuming process: The SSD copies the entire contents of the block to RAM, changes the data in the block, erases the original block of data on the SSD, and writes the changed block back to the SSD.