Solid State Drives Explained

Solid state drives, or SSDs, are popping up more frequently in notebooks, most notably in the Apple MacBook Air and the Lenovo ThinkPad X300. Thanks to a lack of moving parts, these flash-based storage solutions consume less power than traditional hard disks (check out our blog post, SSDs Better for Battery Life) and offer superior durability. We spoke with Steve Weinger, senior manager of flash memory marketing at Samsung, to get a better understanding of SSDs as well as a look into the future of this technology.

What makes SSDs different and how do they work?

Traditional hard drives have a spinning platter and a head that reads data from the platter. Solid state drives, however, have no moving parts. So SSDs can typically withstand small drops off of surfaces such as coffee tables better than a hard disk drive (HDD). Instead of the traditional innards, SSDs have NAND flash chips and a controller.

Solid state drives also consume less power than traditional disk drives. For example, a 2.5-inch Samsung SSD consumes less than 1 watt of power during active use, compared with the 2.1 watts that a standard 2.5-inch HDD consumes.

By and large, SSDs are faster than hard drives but not in all applications. “In sequential reads, the SATA II SSDs that are out today can read at about 100 Mbps per second and write at about 80 Mbps,” Weinger said. “Hard drives have a range; a 7,200-rpm hard drive can read in the area of 60 Mbps and write at about 60 Mbps. A SSD’s real-time improvement is with the random reads.”

Where will users see the most increased performance?

Weinger argues that faster boot and shutdown times are the most noticeable improvements in SSDs, but users will also see speedier application launch times. “Hard drives get fragmented and slower over time; you don’t see that lag over time with solid state drives,” he said.

On our tests, we found that a 32GB SSD from MTron booted Windows Vista in 38.5 seconds, while a 5,400-rpm Western Digital Scorpio was able to boot the same OS in 42.9 seconds—not much of a speed increase. However, we did see an increase in the sequential read/write times where the SSD was 33.5 Mbps and 31.7 Mbps faster, respectively. The SSD was also able to randomly seek data at 0.2 ms, as opposed to the Western Digital’s 17.6-ms seek time.

What is the expected maximum capacity for SSDs in 2008?

Samsung and MTron announced 128GB SSDs this year, while others, including PQI and Super Talent, offer 256GB models. “[Samsung] invests a lot of money into NAND flash and shrinking our dies and growing our densities,” Weinger explained. “At a component level, we’ve been able to double our density every year for ten years.”

What is the average battery-life savings of an SSD?

Weinger said that during Samsung’s testing, he saw an average battery life improvement of about ten percent. That’s because, while SSDs consume less power, LCDs and other components can still suck battery life. Extended battery life is dependent on the components working together to consume the least amount of power. In other words, you should think long and hard before dropping $1,000 on an SSD if you’re expecting a huge endurance boost. You may be better suited by adding an extra battery to your shopping cart instead.

What’s the max number of writes/reads or life expectancy for an SSD?

Samsung and SanDisk SSDs have a two-million-hour mean time between failures (MTBF). “That’s a much greater number than a hard drive has today,” Weinger said. By comparison, the WD RE2, a high-performance Western Digital SATA drive, has an MTBF of 1.2 million hours. SSDs move data around on the drive itself instead of going after the same cell, which allows the drives to have a longer life span than HDDs. “On NAND chips built today with single-level cell chips, we have 100,000 read/writes per cell. We’re talking about millions of cells on a solid state drive. Each cell can be written 100,000 times.”

What’s the difference between single-level and multi-level cell technology?

Multi-level cell technology (MLC) allows two bits to be stored in each cell on the hard drive, while single-level cell technology (SLC) allows just one.

Can you add an SSD to an existing notebook, and if so, what do you need to adjust?

“An SSD should be a drop-in replacement for a hard drive,” Weinger explained. Since solid state drives don’t get fragmented like HDDs do, you don’t have to worry about defragging them, so you can turn off any scheduled defragment programs.


Which manufacturers have notebooks with SSDs in them, and how much do they cost? 

Alienware, Apple, ASUS, Dell, General Dynamics, HP, Lenovo, Motion Computer, and Sony sell systems with Samsung SSDs as an option. MTron and SanDisk are also major players, and Intel will soon be offering its own SSDs. To add a 64GB SSD to a Dell XPS M1730, you’d have to pay an additional $900. Likewise, adding one to an Alienware Area-51 m15x or an Apple MacBook Air would cost you an additional $700 and $1,299, respectively. Across OEMs, that’s an average of $966 just to add a 64GB SSD.

What’s the future of the SSD? 

“I don’t want to say its going to be a standard. SSDs and hard drives are going to exist together,” Weinger explained. SSDs offer some added value. For instance, they have no noise, and there is virtually no heat. “We do feel that SSDs are going to play a major role in the notebook world.” And he may be right. According to American Technology Research, by 2011 nearly 40 percent of the notebooks in the world will be using SSD. 

How much will the prices of SSDs drop over the next few years?

Joseph Unsworth, research director of NAND Flash Semiconductors for Gartner, said we can expect a 64GB SSD to cost about $450 in 2009 and only $200 in 2010. “It is important to note that these will be based on multi-level cell technology and not the current single-level cell technology, which is more than double the price for the flash,” Unsworth noted, adding that “performance and quality have the potential to vary considerably between vendors, which is why it’s difficult to come up with an average price.”