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The quest for flawless SSD performance: will it ever succeed? One thing's for sure, intriguing but frustrating new problems seem to bubble up just as fast as existing issues are flattened out. The question is, therefore, how big a step in the right direction is the new Corsair Force GT 120GB?

On paper, it's state of the art. For starters, it packs 120GB of synchronous flash memory. More expensive than the asynchronous alternative, one of its main supposed advantages involves performance in incompressible data transfers.

We'll come to the details presently, but the key factoid here is that incompressible data is perhaps the greatest weakness of what might just be the best SSD controller on the planet, the SandForce SF-2281. And that just so happens to be the controller found in the Corsair Force GT 120GB. So that's one problem sorted. Well, maybe.

As it happens, the SF-2281 has a few other foibles. But like we said, despite several years of progress and honing, flawless SSD performance remains an ambition, not a reality. Like most current SSDs, the Corsair Force GT supports the Windows 7 TRIM command and therefore shouldn't suffer from chronic performance degradation over time. Another performance hurdle ostensible vaulted, then.>

It also packs the SATA 6Gbps I/O interface. That matters because SSD performance is now outstripping the bandwidth provided by SATA 3Gbps. The Corsair Force GT's 555MB/s peak read and 515MB/s peak write performance is certainly way beyond the theoretical capacity of SATA 3Gbps.

The only sligt snag is that the Force GT is not alone. Several other drive makers, including OCZ, Patriot, Kingston and others offer similar SandForce-based, SATA 6Gbps-capable technology. Then there are several much-improved drives based on non-SandForce controller, including Crucial's M4 drive. Much will thus depend on pricing and Corsair's fine-tuning efforts.

Synching sand

The new Corsair Force GT 120GB has plenty of competition and one of its most obvious foes is Corsair's own Force 3. After all, it too has the SandForce SF-2281 controller and 120GB on NAND flash memory.

It all comes down to a single missing letter 'a' for the Force GT. We speak of the great synchronous vs asynchronous memory debate. The simplest way to appreciate the difference between the two is to view them as SRAM and DDR RAM, the latter in both cases offering two data tranfer per cycle to the former's one.

Synchoronous NAND memory shifts data on both the rise and fall parts of the signal wave. You might think that double data rate makes synchronous flash twice as fast. Actually, in extreme cases it's better than that. Asynchronous memory is limited to 50MB/s per channel compared to either 133MB/s or 200MB/s for the two most prevalent synchronous flash implementations.

However, the real-world performance gap is rarely, if ever, that yawning. To understand why, it's worth taking a look at the SandForce SF-2281 controller. It packs eight memory channels and kick out a maximum overall data transfer of 400MB/s with asynchronous memory.

However, the SF-2281's party trick involves compressing data long before it needs to be written to the flash memory chips. And that means the 50MB/s limitation can be sedestepped. At this point, however, things get a bit complecated. Some data types are made of incompressible data.

In fact, many of the largest and most data-intensive files, such as music, images and video, are stored in pre-compressed - and therefore incompressible as fas as teh SSD controller in concerned - formats. All of which means the Force GT's synchronous memory ought to give it a performance advantage to justify the price premium.

Magic bullet?

Whatever SSD you go for, it ain't gonna be cheap. In the context of SandForce-powered drives, you could argue that there's no point in risking a false economy courtesy of a cheaper model with asynchronous memory. Better to spend that little bit more for the full synchronous treatment.

As the bencmarks demonstrate, the extra $54 or so for the Corsair Force GT over the mostly Force 3 does buy you more performance. Okay, the peak read and write scores of 557MB/s and 518MB/s aren't a huge step forwared. But then we weren't expecting that.

No, much more dramatic is how the Force GT lifts performance in the AS SSD incompressible data read test from just 204MB/s to fully 503MB/s. Result, you might say.

However things are slightly less salubrious in the incompressible data write benchmark. The Force GT does have the edge. But at 164MB/s to 142MB/s it's not a dramatic improvement. It's similar story in the random access test. Again, the extra $65 doesn't buy you a big chunk of extra performance.

What's more, the competition in the form of drives powered by the Marvell 9174 controller, such as teh Crucial M4, hose the Force GT when it comes to incompressibel writes. They're pretty much in the same ballpark of random access, too. Still, what really matters is real-world thoughput, not synthetic tests and the Force GT delivers some solid numbers in application tests. It absolutely trashes the Force 3 and Crucial M4 in game install bencmarks.

But what about the performance of two Force GT's in striped RAID 0 config? Well, the magic 1GB/s for both sequential reads and writes is attainable. You'll get close to 1GB/s for incompressible reads, too. What you won't get is all-round performance that reflects those massive peak numbers. On the synthetic side, teh AS SSD benchmark reveals that 4k random access is barely boosted when you pair drives up. Similarly, app performance doesn't exactly explode.

So, are there any downsides? Well, the big problem is TRIM support for RAID setups, it's been addressed by Intel on the chipset side recently. But still waiting for an update for Windows 7. At this stage, we don't expect anything before Windows 8 appears and even then it might mean an upgrade to 8 rather than a patch for Windows 7.

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