The controller in an SSD is in control. Without it nothing would be read, written, or stored. It makes the difference in benchmark testing and day-to-day usage. Here’s a quick look inside a controller.
Job of the Controller
SSD data is stored in flash memory chips. The controller executes a read or a write to the flash then firmware manages and directs the process.
Flash chips consist of thousands of cells, and each 4K byte of cells is called a page, which is the smallest structure that’s readable/writable in a SSD. When the controller executes a write command, it looks for the first available empty page and writes to that page—continuing to move from one page to the next until it completes the write.
If all pages are available—as with a brand new SSD—it’s called a clean state. That’s when you get your best performance in the write process. But if there’s not that many empty pages available and they are scattered around in different blocks—typical in a used drive—it’s called a dirty state. When it’s dirty the controller has to search for open pages to write to. This is a slower process and you usually get degraded performance.
You find the same issues with the read process. In a clean state, all data is stored closer together. Locating data and reading it back becomes quick and easy but in a dirty state the controller has to spend more time searching and collecting fragmented data and, again, it’s a slower process and performance suffers.
The job of the controller is to perform these read/write tasks with every type of data with a high degree of accuracy, speed, and reliability.
Marvell Controller or SandForce Controller?
Most of the leading SSD manufacturers use either Marvell or SandForce controllers. SandForce uses the same firmware regardless of brand—and it’s important to note that the SandForce firmware is not subject to modification. This may be an advantage for manufacturers looking to cut corners, but modification is essential if you’re building a drive to set a new standard of performance.
Imagine a bunch of high performance cars that are different in almost all aspects—body style, suspension, wheels, paint—everything except for what’s under the hood. There you find the same identical stock engine for all cars. That’s not a very exciting scenario. A SandForce controller lends itself to that type of scenario—pop open the cover and you’re going to find the same stock firmware regardless of brand. No mods allowed.
Marvell controllers on the other hand do not come pre-packaged with stock firmware. Sourcing controllers from Marvell requires an SSD manufacturer to make a substantial investment in time and resources, including assembling a team of specialized firmware engineers. But with the right planning and execution, they yield a fully custom and differentiated product, such as Plextor’s SSDs with TrueSpeed.
Main Difference Between Marvell and SandForce
One of the main differences between Marvell and SandForce is how they deal with compressible or incompressible data. Compressible data includes system files, application files, associated user files, and PC utilities—the usual stuff.
Incompressible data includes software-encrypted files, ZIP files, JPEGs, voice, videos, and movies. SandForce doesn’t fare well with incompressible data.
SandForce is better at handling everyday tasks using compressible data. SandForce’s strength—or limitation, depending on your needs—is the ability to compress data before it gets into the flash memory. This may achieve impressive read/write speeds, but only if the data on the drive is compressible.
Marvell achieves superior read-write performance with both compressible and incompressible data in clean or dirty state. Handling incompressible data is essential to the gamer where quick and almost instant loading of complex scenes is critical in tournament play, especially with online competition. Or consider a photographer where the ability to transfer tens of thousands of pictures a week quickly and efficiently is essential, saving time and increasing productivity.
Plextor’s Modified Marvell Controller
For the M5 Pro, Plextor uses the new Marvell 88SS9187 modified with exclusive Plextor True Speed technology that prevents performance degradation when the SSD enters dirty state. True Speed ensures equal speed for all types of data and maintains sustained performance levels in the long term.
Also, Plextor’s brand new AES Encryption and True-Protect technologies gives businesses and system integrators access to the highest level of encryption and multiple layers of data checking for absolute data accuracy.
These custom modifications and standard-setting features would be impossible with a SandForce device.
Every Plextor SSD undergoes the industry’s most extensive preproduction testing to ensure unsurpassed reliability. Tests include a 20-hour High Temperature burn-in test and the rigors of the industry’s premier-level FLEXSTAR testing machine to simulate real working environments. As a result, Plextor SSD devices have the industry’s lowest average annual failure rate (0.5%).
StorageReview.com was emphatic in stating: “We place extra emphasis on brands who own the SSD controllers they use. The benefits of using an in-house controller are massive from both a drive performance and reliability perspective.” They went on to say: “With in-house engineers and unique software, Plextor is getting more out of Marvell-based SSDs than just about anyone else.”
Marvell or SandForce? What’s your choice?