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SSD performance scaling across the spectrum

Size matters, but how much?

Let's be honest. In the PC world, size matters. This is true not only for the height of ATX towers, but also for the thickness of ultrabooks. The size of one's SSD is important, too. In addition to defining how many applications, games, and data can enjoy the speedy access times of solid-state storage, an SSD's capacity plays a large role in determining its overall performance.

Drive makers admit as much on their datasheets, which routinely list slower performance specifications for lower rungs on the capacity ladder. Writes are affected more than reads, the MB/s and IO/s ratings say, and models around 256GB are typically the fastest of each respective breed. As one might expect, it's these higher capacity points that are first sampled to the press. They're not the capacities most folks end up buying, though.

The price of flash memory has fallen in recent years, yet high-capacity SSDs remain expensive luxuries at $300 and up. Drives in the 120-128GB range are much more attainable, with street prices comfortably below $200. 64GB variants are easily affordable at around $100, so they're especially tempting as system drives for desktops and streamlined notebooks.

We've already explored how contemporary 120-128GB SSDs compare and how their performance scales up to higher-capacity models. Today, we're moving in the opposite direction with a stack of 64GB and smaller SSDs. We've tested these Blue Light Specials to complete the performance scaling picture. Our test results now run the capacity gamut, from 64GB or less to 256GB or more. We've also thrown pairs of 64GB drives into RAID 0 arrays to see whether it's worth doubling up on cheaper SSDs or splurging on a single, higher-capacity model.

So, yeah, we have a mountain of performance data spread across pages of pretty graphs, plus the usual value analysis to help make sense of it all. And thousands of dollars worth of SSDs photographed in pretentious poses. This article is the culmination of quite literally months of testing in the Benchmarking Sweatshop, and I'd really like to get on with it. Shall we?

And then there were four
There were five drive families represented in our first SSD scaling article, but we've had to cut back to four because the Intel 510 Series is only available in 120GB and 250GB capacities. Since it relies on older 34-nm flash memory, the 510 Series is overdue for a 25-nm replacement, anyway. That's about all I can say on that subject for now—but stay tuned.

  Interface Controller NAND Cache Warranty
Corsair Force Series 3 6Gbps SandForce SF-2281 25-nm Micron async NA 3 years
Corsair Force Series GT 6Gbps SandForce SF-2281 25-nm Intel sync NA 3 years
Crucial m4 6Gbps Marvell 88SS9174 25-nm Micron sync 128MB 3 years
Intel 320 Series 3Gbps Intel PC29AS21BA0 25-nm Intel 64MB 5 years

Without the Intel 510 Series, we're still left with a range of drives covering the most popular configurations available today. Two of these configs are exclusive: the 320 Series is only available from Intel, and the m4 uses a unique mix of chips offered by Crucial alone. Corsair's Force SSDs are a little different. They represent a couple of SandForce-based configurations also offered by a number of other drive makers, including OCZ and Kingston.

The Force Series 3 is the slower of the two SandForce configs due to its asynchronous NAND, which isn't as exotic as the synchronous stuff found in the GT model. Both drives rely on the same SandForce SF-2281 controller. We examined this chip in depth in our early look at the OCZ Vertex 3, so I won't burden you with all of the details here. It's worth noting that SandForce uses an on-the-fly compression scheme to speed write performance and reduce NAND wear. Unlike other SSD controllers on the market, the SF-2281 doesn't make use of separate DRAM cache memory. Otherwise, the chip has a 6Gbps Serial ATA interface and eight memory channels.

Marvell provides the controller in Crucial's m4. The 88SS9174 chip is familiar from the Intel 510 Series and the old Crucial C300, but in the Crucial m4, it's paired with the latest 25-nm flash. This memory comes from the same synchronous class of NAND found in the Force GT, making the m4 a similarly premium solution. As we explained when we first looked at the m4, the Marvell chip matches the SandForce controller with a 6Gbps interface and eight memory channels. There's no compression voodoo at work in it, though.

The Crucial m4 has double the cache memory of Intel's 320 Series, whose 3Gbps SATA interface hails from the previous generation. Indeed, the origins of the Intel PC29AS21BA0 controller at the heart of the 320 Series can be traced all the way back to the original X25-M, which came out more than three years ago. The chip has ten memory channels, although due to their vintage, each one is likely slower than a modern equivalent. Nevertheless, the drive is outfitted with new 25-nm NAND that we suspect is of the asynchronous variety. (Intel keeps certain details about the 320 Series to itself.)

Since our storage test rigs feature 6Gbps SATA controllers, the Intel 320 Series has a pretty big handicap right out of the gate. Intel isn't selling the drive as a performance leader, instead focusing on reliability. This is the only drive of the lot with five years of warranty coverage—two years more than the industry norm.