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A six pack of solid-state drives compared


Can any top the X25-M?
— 9:17 PM on May 17, 2009

For years, solid-state drives have been great in theory, but a little problematic in practice. The rationale for replacing mechanical media with solid-state silicon certainly seems sound. Without moving parts, SSDs can be far more durable and shock-tolerant than drives that have to contend with platters spinning at thousands of revolutions per minute. The lack of mechanical latency allows SSDs to seek several orders of magnitude faster than traditional hard drives, as well.

The first flash-based solid-state drives delivered on those fronts, and they even added an attractive element of low power consumption to the mix. However, these drives were saddled with a few rather serious problems. While even the first flash drives boasted near-instantaneous seeks, their sustained transfer rates were quite slow. Initial capacities were relatively small, as well, and then there was the associated cost, which can only be described as exorbitant.

In practical terms, then, early SSDs were pretty much a failure.

But the nice thing about solid-state drives is that, in theory, Moore's Law should eventually solve all of the above problems. Indeed, semiconductor progress has effectively dealt with most of them already. Thanks to smaller and denser memory chips, drives with capacities up to 256GB are easy to come by today. Such capacities may not match the multiple terabytes one can get with mechanical desktop drives, but they are more than adequate for most folks. They may even be sufficient to handle even a PC enthusiast's collection of OS, application, and game files.

Meanwhile, smarter drive controllers have improved SSD throughput by addressing more memory channels in parallel. Intel's X25-M has already shed the solid-state legacy of poor sustained transfer rates.

That's two for two so far, which leaves us only with price. And wouldn't you know, the picture doesn't look all that dire. Take the X25-M, for example. Intel's first SSD debuted just eight months ago in an 80GB flavor for just under $600. Thanks to a steady diet of price cuts, you'll pay closer to $325 for the very same drive today. Plenty of cheaper options are available, too, with some lower-capacity SSDs dropping below $100.

Solid-state drives still have much progress to make on the cost-per-gigabyte front, but depending on your priorities and budget, one could argue that, for SSDs, pratice has finally caught up with theory, resulting in some good and practical storage solutions. Thus, now is a perfect time to check in on the market to see what's available. We've wrangled half a dozen SSDs from Corsair, OCZ, Samsung, Super Talent, and Transcend to see how they stack up against each other—and against Intel's X25-M standard.


Lining 'em up
We're focusing our attention today on solid-state drives that use multi-level cell (MLC) flash memory. MLC memory has slower write speeds and a lower write-erase cycle tolerance than single-level cell (SLC) flash, but it's considerably cheaper, which is why MLC chips have become the de facto standard for consumer-level solid-state drives. SLC flash is predominantly confined to more expensive enterprise-class drives like Intel's X25-E Extreme.

There's much more to SSDs than their choice of flash memory types, though. As we saw with the X25-M, a good drive controller design can have a major impact on performance. Intel has so far kept its SSD controller in the family, sharing it only with partners like Kingston, who are selling re-badged X25-series drives. There are other drive controller players in the market, though.

Among the rest, Samsung is easily the most established. Samungs mainstream 256GB SSD, the PB22-J, uses a disk controller of the company's own design, and you'll find the same chip in Corsair's new P256. In both cases, the Samsung controller is paired with 128MB of DRAM cache.

Korean firm Indilinx has only recently entered the SSD market, and its latest controller can be found in OCZ's Vertex and in Super Talent's UltraDrive ME. Super Talent silkscreens its own name onto the UltraDrive's controller chip, but we can confirm that it is indeed Indilinx silicon inside. Both Indilinx implementations employ DRAM cache memory of 64MB. That's still double the cache available even in most high-end desktop drives.

In addition to its high-end Vertex drive, OCZ also sent over an SSD from its mid-range Apex series. Rather than using a single controller, the Apex combines a trio of JMicron chips in an internal RAID 0 configuration; a pair of JMF602B controllers manage the flash memory, while a JMB309 picks up striping duties. The JMF602B also makes an appearance in Transcend's awkwardly-named TS32GSSD25S-M, although only in a single-chip configuration without internal RAID. Since the JMicron controller doesn't support separate cache memory, neither the Apex nor the Transcend drives have DRAM chips onboard.

Capacity Cache Controller Max reads Max writes Warranty Street price
Corsair P256 256GB 128MB Samsung S3C29RBB01-YK40 220MB/s 200MB/s 2 years
OCZ Apex 120GB NA JMicron JMF602B/JMB390 230MB/s 250MB/s 2 years
OCZ Vertex 120GB 64MB Indilinx IDX110M00-LC 250MB/s 180MB/s 2 years
Samsung PB22-J 256GB 128MB Samsung S3C29RBB01-YK40 220MB/s 200MB/s NA NA
Super Talent UltraDrive ME 128GB 64MB Super Talent STT-C-BF-GX 200MB/s 160MB/s 2 years
Transcend TS32GSSD25S-M 32GB NA JMicron JMF602B 150MB/s 90MB/s 2 years

Controllers and cache configurations largely determine SSD performance, but before we put today's contenders to the test with an extensive suite of benchmarks, it's worth perusing each drive's purported maximum read and write speeds. While not necessarily indicators of a drive's sustained throughput in the real world, these theoretical peaks do provide fodder for forming initial expectations.

The OCZ drives claim the highest peak transfer rates, with the Vertex apparently capable of reading at 250MB/s and the Apex equaling that speed with writes. Unlike the others, the Apex's maximum write speed is higher than its peak read rate—likely an artifact of the drive's funky internal RAID 0 config. There's only a 20MB/s gap between the Apex's max read and write rates, too; that difference grows to 70MB/s with the Vertex, which can only write at up to 180MB/s.

With peak read and write rates of 220 and 200MB/s, respectively, the Corsair and Samsung drives appear to be more balanced than the Vertex. Super Talent's UltraDrive ME, on the other hand, looks to be a little slower overall. The UltraDrive's read and write speed maximums are much higher than those of the Transcend drive, though. To be fair, the Transcend is by far the cheapest drive of the bunch. The Transcend also has the lowest storage capacity of the lot—and more importantly, half as many flash chips as the other drives in this round-up.

Of course, Transcend does make higher-capacity SSDs. Corsair, OCZ, Samsung, and Super Talent also offer more affordable drives with lower capacities. All seem to agree on covering their drives with two-year warranties. That's a year's less coverage than one typically gets with standard desktop or notebook drives, and high-end drives like WD's Black Series offer up to five years of coverage.

Samsung's PB22-J is the only exception on the warranty front because it's not actually sold as a bare drive. The PB22-J is only offered in complete systems from the likes of Dell, HP, and others, and those vendors determine the drive's warranty coverage and effective price. Worry not, though. The PB22-J is all but identical to Corsair's P256, which is available for sale as a bare drive.