Pop quiz answers: Solid-state drives

Nearly 500 people took IT Dojo's pop quiz on solid-state drives (SSDs). Here's a list of the correct answers and a breakdown of how well those who took the quiz scored.

As of grading time, nearly 500 people had taken our solid-state drives quiz. If you haven't had a chance to take the quiz, I encourage you to try your luck, before reading the answers below. Now, on to the answers!

No moving parts

True or False: Like conventional hard drives, solid-state drives are electromechanical devices.

The correct answer is: False and 88 percent of those who answered the question got it right. The term "electromechanical" refers to devices that use both electrical and mechanical parts. Unlike traditional hard drives, which contain spinning platters and a movable actuator arm, solid-state drives contain no moving "parts".

In this quiz's discussion thread, TechRepublic member Dr Dij argued that solid-state drives actually do have moving parts, but "not in the convention sense." According to Dr. Dij, "the doping atoms in transistor junctions are subject to atomic migration." While it's true that the integrated circuits within solid-state drives are effected by atomic migration—the movement of atoms from their original position due to the flow of electrical current (electromigration) or the existence of temperature gradients (thermomigration). I think it's safe to assume that most individuals who took this quiz correctly interpreted my use of the term "parts" to exclude atoms.


Current solid-state drives can use which of the following memory technologies to store information?

The correct answer is: NAND Flash or SDRAM and 73 percent of those who answered the question got it right, as shown. Current solid-state drives use either non-volatile NAND Flash memory (the kind commonly used in USB flash drives) or volatile SDRAM (used for a variety of memory applications, including computer RAM modules).

Volatile SDRAM requires constant power

Which of the following solid-state drive technologies requires constant power to store information?

The correct answer is: SDRAM but unfortunately the correct quiz answer was printed as "SDRAM or NAND flash memory" and was therefore trickier than it should have been. Although the answer, as printed is technically correct because of the "or", I had intended for the answer to be printed "SDRAM." Thanks to NickNielsen for catching the error and to The Scummy One for pointing out the answer's technical correctness. As the answer was tricky, but not technically incorrect, I left the answer as it was originally printed. Leaving the answer also ensured NickNielsen and company's comments wouldn't seem out of context. As I'm now officially releasing the answers, I am going to update the answer.

Despite the tricky answer, 48 percent of those who answered the question chose the correct answer. SDRAM is volatile and requires a constant power source to store information. Purely SDRAM-based solid-state drive must contain a power source (such as a battery) separate from the main supply to prevent data loss during a power failure. Because of their volatile nature, purely SDRAM-based drives aren't really suited for long-term data storage.

No indefinite lifespan

True or False: Because they have no moving parts, solid-states drives have an indefinite lifespan.

The correct answer is: False and 74 percent of the people who answered the question got it right. Although RFink asserted that I used "indefinite", when I should have used "infinite", it appears most users clearly understood my use of "indefinite" to imply "not definite; without fixed or specified limit; unlimited" (Dictionary.com).

Although solid-state drives lack moving parts, they won't last forever. While flash memory can support unlimited read cycles, the lifespan of NAND flash based-drives is limited by the number of erase-write cycles each block can withstand. Unfortunately, there is no single standard for measuring flash endurance. Memory manufactures usually rate their products somewhere between 100,000 and 1,000,000 write cycles. To mitigate write-cycle limits and extend the drive's life, most manufactures use techniques such as wear leveling or block management. Unless you continuously erase and rewrite the entire drive, flash-based SSDs will likely last for the same amount of time, if not longer, than conventional hard drives. But, you should always have a backup.

SSDs currently more expensive

Which of the following is not a benefit of current solid-state drives over conventional hard drives?

The correct answer is: Lower cost and 79 percent of those who answered the question got it right. Although prices are dropping, solid-state drives are currently more expensive than traditional hard drives. A 32GB NAND flash-based SATA SSD will cost between $500 and $600. A 500GB, 7200 RPM SATA hard drive goes for between $100 and $150. That's a big premium for the SSD.

Learn more about solid-state drives

For more information on solid-date drives, check out the following resources:

About Bill Detwiler

Bill Detwiler is Managing Editor of TechRepublic and Tech Pro Research and the host of Cracking Open, CNET and TechRepublic's popular online show. Prior to joining TechRepublic in 2000, Bill was an IT manager, database administrator, and desktop supp...

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