OCZ RevoDrive 3 X2 480GB £1296
15th Sep 2011 | 08:30
Professional-class SSDs don't come any quicker
Too much performance is a nice problem to have. It is still a problem though, especially in the context of some solid state drives. But not the new OCZ RevoDrive 3 X2 480GB.
OCZ claims it's capable of read speeds up to 1.5GB/s. That's monumental bandwidth by any measure and much, much more than even the latest SATA 6Gbps interface can handle. In practice, a mere 500MB/s of sequential bandwidth can be enough to saturate a SATA interface.
That's why drives powered by the latest SandForce SSD controller, such as OCZ's own Vertex 3 or Corsair's Force GT, can't quite reach their full potential on a SATA connection. There's simply not enough available bandwidth.
But the OCZ RevoDrive 3 X2 480GB is no ordinary SSD. It sports no less than four of the snazziest Sandforce SF-2281 controller chips. It is, in effect, four 120GB Sandforce-powered SSDs running in a parallel RAID array for maximum performance.
Crucially, however, it hooks them in via a speedy four-lane PCI Express connection. On paper, that allows up to 2GB/s of bandwidth. In other words, if the RevoDrive 3 doesn't deliver on its theoretical capabilities, it won't be able to point the finger at the SATA port. And some capabilities the Revodrive has, if OCZ's performance claims are accurate.
The headline figures include sequential read and write figures of 1,500MB/s and 1,225MB/s. Those are very, very big numbers. Not long ago, anything over 100MB/s seemed quick. But with this drive, OCZ is dragging storage into the GB/s era.
However, it's worth remembering we're talking about an SSD with SandForce controllers. Those peak numbers involve compressible data. Throughput with incompressible data will inevitably be lower.
Then there's the question of random access rather than raw sequential bandwidth. OCZ pegs the RevoDrive 3 X2 480GB at 200,000 IOPs for 4k aligned random writes, which bodes well. But as we've learned, when it comes to SSD random access performance, the practice doesn't always match the theory.
Performance is nothing without control, which is where OCZ's original RevoDrive PCI-e SSD fell short. It didn't support TRIM command or SMART data. Together these features help keep SSDs fast and fit. The good news is that the new RevoDrive 3 adds support for both. We'll get into the details momentarily, but the simple version is that it's OCZ's VCA 2.0 (Virtual Controller Architecture) software layer that works the magic. The bad news is that issues on the OS side remain. Again, more on that in a moment.
What we have, therefore, is a storage solution that seems to come tantalisingly close to offering the complete package. It's fully bootable. It's silly fast. And it delivers on its half of the TRIM support equation. But is it really that much better than an ordinary SSD or conventional RAID array?
First, a little lesson in nomenclature. The 'X2' in OCZ RevoDrive 3 X2 480GB means this is a double-decker card with a pair of PCBs. Think of it as two SSDs per board. Together, the two boards form a single drop-in PCI-e board in four-lane format.
So, you'll need at least one PCI-e port of minimum four-lane spec available in your PC. The RevoDrive 3 X2 will, of course, happily hook up to an eight or 16-lane PCI-e socket, though there are no performance benefits to be had.
Each of the two PCBs has a pair of cutting edge SF-2281 SandForce controllers and 240GB of asynchronous NAND flash split into 16 chip arrays. For the record, the flash chips are 25nm Micron items. That means lower write/erase longevity of around 5,000 cycles compared with the typical 10,000 or more cycles of previous generations of flash memory.
Exactly what impact this will have on SSD survival rates remains unclear. Clever wear-levelling algorithms do much to nullify the effect of fewer available cycles. What's more, the aggressive use of data compression by the SandForce controller further mitigates wear compared with other controller chipsets. But the overall trend towards fewer cycles still leaves us feeling a little queasy with an SSD that costs more than most PCs.
OCZ has cooked up a software layer that promises several benefits and has given the RAID hardware an overhaul to boot. Gone, therefore, is the convoluted series of chips found in the first RevoDrive that converted SATA to PCI X and then PCI-e. Instead, there's a single chip that channels four SAS ports through to four PCI-e channels and it's much cleaner and simpler.
On top of the RAID chip sits a virtualised software layer known as VCA 2.0. The trick here is to present the four SSDs as a single device and in turn enable TRIM along with SMART data, native command queuing and more.
If it's unprecedented, intergalactic throughput you seek, look no further than the OCZ RevoDrive 3 X2 480GB. Regards sequential read and write performance, the numbers OCZ itself claims are spectacular at 1,500MB/s and 1,225MB/s. But our test results are even better at 1.65GB/s and 1.37GB/s. Think about those figures for a moment.
For starters, the RevoDrive murders the 1GB/s barrier and thus makes mass storage performance that rivals system memory seem a lot more plausible. But the gap between the claimed performance and our results is well over 100MB/s for both reads and writes. The RevoDrive is so fast, its deviation alone from claimed performance is in the same ballpark as the peak performance of an early SSD.
Similarly, these benchmarks make the RevoDrive as much as three times faster than the best available SATA SSDs. Fair to say, then, OCZ's PCI Express technology is a success. Elsewhere, however, the RevoDrive's performance is inevitably more mundane. At least, results like 767MB/s and 457MB/s seem mundane compared to the official performance claims.
We speak here of incompressible sequential performance, a metric which tends to be a weak spot for any drive based on a SandForce controller chip. That's because the impressive peak performance achieved by SandForce drives is partially achieved courtesy of data compression. Compressing data before pumping it into the flash chips means less bandwidth in and out. And that means faster transfer rates. Problem is, many if not most of the really data-intensive file types are incompressible, including movies and music.
But if there's an area where we have more serious concerns about the performance of the RevoDrive, it's random access. Much here depends upon the benchmark you choose to run. Use a test like I/O Meter, which generates perfect 4k files for random access tests and you'll see the RevoDrive come close to delivering on OCZ's claims of 200,000 IOPs.
However, perfectly formed 4k files aren't reflective of the messy business of real-world disk usage and access. In that context, a test like AS SSD's 4k benchmark gives a better idea of the worst case scenario. At 25.9MB/s and 65.8MB/s for reads and writes, the RevoDrive is barely any better than a single OCZ Vertex 3.
As for how all this translates into actual desktop performance, the answer is that the results are mixed. On the upside, the RevoDrive tears through game installations at a scarcely believable lick. It's more than twice as quick as a good single SSD.
However, unpacking .ZIP files reveals the limitations. The RevoDrive is slightly slower than a single Vertex 3. It's also worth remembering that the performance of the RevoDrive will often be limited by source or target destinations for data. Data rates between multiple drives in any PC are defined by the weakest link, not the fastest.
Before we consider how the RevoDrive performance and pricing place it in the broad constellation of SSDs currently, what are the practicalities of using a PCI-e -based board as opposed to a SATA drive?
In terms of installation, the RevoDrive couldn't be much easier. Okay, you'll need to crack open your PC's case – you can't run the drive externally like an eSATA drive. You'll also need to use the 'have disk' method when installing Windows 7. But that's a simple matter of dropping the driver onto a USB key before you start the installation process.
From there on, it's much the same as a standard SATA drive with two small exceptions. First, you'll have to suffer a new status screen within the system boot and post process, which slows start-up times by around three to five seconds. In our testing, the RevoDrive also ran hot, which indicates that there are potential problems with longevity and thermal management.
With all that in mind, should you buy OCZ's exotically priced RevoDrive 3 X2 480GB? If money ain't an object and you're a hands-on sort of PC user, the answer is a qualified yes.
Admittedly, it doesn't blow normal SSDs away by every test, but the overall picture is of a drive that at worst is as quick as anything out there and sometimes in a performance class of its own. In that sense, it's a classic big-money enthusiast component. It's not perfect, but it does deliver some outrageous performance figures.
For everyone else, we're not so sure. The RevoDrive's performance in the nitty gritty random access workloads that make up so much of daily computing isn't as spectacular as the raw throughput numbers would have you believe.
Day to day, we doubt you'd notice the benefit over a conventional SSD. But the biggest issue is the lack of fully implemented TRIM support. OCZ has done all it can to enable TRIM on the RevoDrive. What's now required is an update for Windows 7 from Microsoft.
For now, it's unclear whether Win7 client OSes will ever be updated. And that means we can't give the RevoDrive an unreserved thumbs up.
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