Solid-State Drive Review Roundup -- Performance & Drawbacks

Posted 11/17/2008 at 5:00pm | by David Murphy

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What The Future Holds for SSDs

Expect to see upgrades in controllers and NAND flash push SSD prices lower over time, but don’t hold your breath for either hard drives or SSDs to ever oust the other from the marketplace. According to Michael Yang, flash product marketing manager for Samsung, NAND flash capacities will continue to grow at a rate of 40 to 50 percent each year. This puts SSD development on par with the 40 percent capacity growth touted by top hard drive manufacturers.

A number of SSD manufacturers currently use PATA-to-SATA bridges in their SSDs, but it’s expected that these manufacturers will fully adopt the SATA 3Gb/s standard common to hard drives within 12 months. You can also expect to see performance upgrades to the actual NAND flash memory inside SSDs: In addition to block-size upgrades and an increase in SSD controller channels, read-ahead and caching algorithms will improve the drives’ write performance over the next five years.

Single-layer cell (SLC) and multi-layer cell (MLC) technology will continue to make up the flash cell foundations of solid-state drives. But according to Yang, SSDs will start moving away from the conventional form factors—1.8-inch, 2.5-inch, and 3.5-inch drive sizes—established by the magnetic hard drive market. This could bring forth SSDs of all shapes and sizes, an appealing prospect for notebook vendors that want more internal customization options.

Judging by the Numbers

You might not realize what you’re getting when you purchase an SSD. As we’ve learned from this roundup, the nuances of an SSD’s construction can make a huge difference in its performance.

We found that MLC-based drives just aren’t worth their low prices. While their read speeds are certainly impressive compared to those of the fastest hard drives we’ve tested, poor write performance holds them back. We wouldn’t use an MLC-based device as the primary volume for our operating system, especially since we can get hard drives that offer faster reads and writes at four times the capacity for the same price.

SLC-based drives are a different breed entirely. While their prices can vary from reasonable to outrageous, SLC-based SSDs can deliver a massive performance improvement in general operations thanks to their lower random access read and write rates. We would definitely recommend a less-expensive SSD, such as those from Samsung or OCZ, for a notebook environment. The combination of price and performance is great, and the added reliability—SSDs are less likely to fail than hard disk drives if you drop your laptop—sweetens the deal.

You don’t need this kind of protection in a desktop environment. It’s for this reason, and the capacity-to-cost ratio of even the least expensive SLC SSDs, that we cannot recommend this technology for desktops at this time. Or even for a while—we’d tolerate a 128GB SSD in our rig and would be happy with a 256GB product, but it will take a number of successive capacity improvements before such drives reach an acceptable price point.

All of the SLC SSDs we tested blew past a Velociraptor drive in simulated operating system patterns, as evidenced by the PCMark Vantage scores. But this speedy performance is of little value if Windows plus a game or two completely fills the drive. We’d rather stick with two $300 Velociraptors in RAID 0 right now: Based on our experience, an array of these drives is only 10 percent slower than the real-world performance of Samsung’s $800 SSD but offers nine times the capacity.

There will come a day when solid-state drive technology is a more compelling desktop option. Maybe NAND flash will get cheaper to produce or larger capacity SSDs will start bumping down prices on the lower-capacity end of the SSD spectrum. We can promise you one thing: Don’t expect this turnaround to occur for years. This is only the beginning of the storage war.

Update: Since we published our SSD roundup in our November issue, we've also reviewed Intel's X-25M drive. Here's what Gordon Mah Ung, who reviewed that drive for us, had to say about this addition: 

 You can look at Inte’s 80GB X-25M two ways. From the perspective of laptop users, you finally get desktop performance (and beyond) in your portable. For desktop users, you can get RAID 0 performance without having to run the data risky configuration.

How good a performance? Against the six other SSDs, the Intel’s read speeds were roughly twice that of the closest competitor – the $1,500 Memoright. Even better, the Intel drive is selling for about $600. To give you an idea of how fast the Intel SSD is, a wickedly fast Western Digital 300GB Velociraptor tops out at about 98MB/s in reads. We saw a benchgasmic 206MB/s from the X-25M.

The Achilles’ heel of the X-25M is its write speed. At 64MB/s, it’s very respectable but not great. Oother SSD’s on the same MLC memory type as the Intel drive wrote in the 22MB/s range. The Memoright’s SLC memory let it write at 106MB/s while the Velociraptor burns bits at 98MB/s. However, we’d take the trade off as most users read data more than they write. Intel has an answer for the write speeds with an SLC-based drive that will write in the 200MB/s+ range. Drives using SLC, however, will have less capacity (initially 32GB) and cost a ton more cash.