Best SSD: 6 of the top SSDs on test

Love and loathing in equal measure. So goes the shizzle with solid state drives. On the one hand, SSDs are the final piece of the PC performance puzzle. The best SSDs have removed the final significant performance bottleneck on the desktop and also turned laptops into true desktop replacements.

On the other hand, SSDs are a hard PC component to judge. With processors and GPUs, you can tally up core counts and clockspeeds or compare performance in your favourite apps, confident that published benchmarks will reflect your mileage at home fairly accurately. Not so for SSDs.

Like any emergent technology, things change fast. New SSD tech, including controller chips, firmware and NAND flash chips pop up on an apparently daily basis. That alone would make keeping up with developments tricky enough.

But the thing about SSDs is that you never get quite the same performance twice. Box fresh, an SSD can seem spectacular. A few months in and your PC is a stuttering basket case.

Truly awful SSD performance degradation was consigned to the history books with the drive-cleaning TRIM command in Windows 7, but make no mistake, SSD performance still fluctuates significantly over time and with usage patterns. A drive might be lightning quick at shunting large files around but piddle-poor when it comes to handling lots of random access commands in normal Windows usage.

All of which means it helps to get to grips with the latest controller tech and have a handle on how the best SSDs compare when it comes to a wide range of synthetic and real-world benchmarks.

To that end, we've rounded up a goodly mix of top SSDs, including the hottest controller tech from the likes of SandForce and Marvell. With prices starting under £100, SSDs are no longer a luxury reserved for a lucky few.

A good place to start to learn about SSDs is boning up on the best controller chipsets. In the short time that mainstream SSDs have been available, we've already burned through a huge number of controller chipsets.

Back in 2008, JMicron got a jump start on the market with an early SSD controller chipset that looked great out of the box but soon turned drives into a feeble, stuttering mess under heavy usage. Soon after, Intel wheeled out the X25-M with an in-house controller chipset delivering impressive all round performance and particularly good random access throughput.

However, those first-generation X25-M's had their own problems with wilting performance. Quickly, performance degradation over time became the hottest topic in Solid-dom.

The next big winner was probably Indilinx's Barefoot in 2009, which provided a lower cost alternative to Intel's pricey SSD technology. Of course, late 2009 saw the launch of Windows 7 and with it the introduction of the TRIM command, which is a vital tool for keeping SSDs free from dud data and therefore performing much closer to factory spec.

But perhaps the most successful SSD controller chipset of all came in 2010 from an entirely unheralded outfit known as SandForce. The SF-1200 seemed to have it all: Performance in pretty much any metric you cared to mention and long term reliability. One of SandForce's killer features has been DuraWrite, a technology that compresses data on the fly to increase both performance and longevity.

Along the way, several other controller chipsets have come and gone. Both Samsung and Toshiba, for instance, have rolled out some decent chipsets. And, for a while, updated versions of the X25-M kept Intel in the game. But where does that leave us?

Controlling force

A more recent developments has been the upgrade from 3Gbps to 6Gbps for the trusty SATA storage interface. Unfortunately, the faster standard requires new hardware all round. In other words, you need both a 6Gbps SSD and a 6Gbps-capable mobo.

One of the earliest movers in the 6Gbps market was Marvell with its 9174 controller in the second half of last year. It's still one of the most widely used and best performing SSD controller chipsets out there. With eight channels and support for interleaving, read performance tops out well over 400MB/s second while sequential writes can breach the 300MB/s barrier. Impressive stuff.

At least, it is until you snatch a glance at the capabilities of SandForce's new SF-2200 chipset, introduced earlier this year. On paper, it takes everything that's great about the old SF-1200 chips and adds SATA 6Gbps support for seriously searing performance. Sequential performance beyond 500MB/s for both read and write is possible, opening up the prospect of dual-drive arrays capable of the magic one gigabyte per second. That's more or less ten times the performance of the best magnetic drives of just a few years ago.

As good as the latest CPUs and graphics cards are, even they can't deliver performance gains as massive as that.

Future solids

The SandForce SF-2200 and Marvell 9174 are the best controllers available now but there are a couple of interesting alternatives either available now or coming soon.

Intel's in-house SSD development has gone slightly off the rails of late. The consequence is that its new SSD 510 uses the Marvell controller. However, the third-generation in-house technology, known as SSD 320 has now arrived. With maximum read and write performance of just 270MB/s and 220MB/s, it's hardly a performance leader. But that's forced Intel to price it up much more competitively.

Another option on the close horizon is the upcoming Indilinx Everest controller. It's not appeared in consumer SSDs yet, but promises peak performance close to the SandForce SF-2200 series. As it happens, Indilinx was recently bought by consumer memory specialist OCZ. So, we're hopeful for some Indilinx-powered drives from OCZ soon.

That should prevent SandForce from dominating the market. But even if you're au fait with the fanciest controller chipsets, there are a few SSD foibles to be aware of. After the controller chipset, the next most important component is the flash memory itself.

Almost all consumer SSDs use some form of multi-level cell (MLC) NAND memory. However, there are different varieties. One key distinction is between asynchronous and synchronous MLC NAND.

The former is cheaper but limited to 50MB/s per controller chipset channel. Current synchronous NAND is good for up to 200MB/s per channel with 400MB/s NAND chips due out soon. Factor in the eight channels available in most controller chipsets and the result is 3.2GB/s performance coming to an SSD near you fairly soon. Good stuff.

Longevity is another key issue and looking even more critical with 25nm MLC NAND memory. Where 34nm NAND was rated at 10,000 write-erase cycles, the best latest 25nm chips are claimed to be good for half that figure. Some are rated at just 3,000. While that doesn't sound like a lot, the combination of redundant cells with advanced wear levelling algorithms means heavily used SSDs should last for at least five years.

Even so, the moral of the story is that SSDs don't go on forever. But are still much more tolerant of physical knocks and are way less likely to drop dead unexpectedly. SSDs ain't perfect, but they're by far the best storage technology available today.