Articles: Storage

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Our recent comparative review of solid state drives based on the SandForce SF-2281 controller proved that there are performance-relevant factors other than the controller itself. The choice of NAND flash memory and its architecture can also be highly important. The SF-2281 being an eight-channel controller, the majority of SSDs (except for entry-level models with a capacity of less than 120 gigabytes) utilize all eight. However, the number of chips and NAND devices on each channel can affect the resulting performance, too. Roughly speaking, the more flash memory devices are connected to each controller channel, the better. This is just how the internal algorithms of the SandForce controller work.

One consequence is that the SF-2281 makes SSDs faster as they grow larger in storage capacity. You may have noticed that specifications of 240GB SSDs are higher than those of their lower-capacity cousins. That’s not just a marketing trick serving to promote large-capacity products. Practical tests indicate that 120GB SSDs indeed find it hard to compete with 240GB ones. That's why Corsair's Force 3 and Force GT disks weren’t brilliant in our previous review. These series were just represented with lower-capacity models which fell behind their 240GB opponents (OCZ Vertex 3 Max IOPS, Kingston HyperX and OCZ Agility 3). We now want to make our amends to Corsair as the company has provided us its 240GB Force 3 and Force GT products.

So, in this review we are going to see the difference between solid-state drives of different storage capacities, taking the SandForce-based Corsair Force 3 and Force GT series as an example.

Let’s first take a look at each product we’re going to test.

Corsair Force Series 3 240GB

Corsair’s entry-level Force 3 series is based on a second-generation SandForce controller. The low performance of the inexpensive NAND flash memory of this SSD is supposed to be masked by the controller's advanced operation algorithms. Being one of the key features of the SF-2200 series, the algorithms ensure on-the-fly data compression in order to keep the data-transfer rate high even with slow flash memory. Moreover, this allows to increase the reserve space to improve the SSD’s reliability. The resulting product offers acceptable performance at $1.3 to $1.4 per one gigabyte of storage, which is a real bargain.

The Corsair Force 3 240GB is shipped in a small, demurely designed box.

Besides the SSD proper, the box contains a guide with fasteners for installing this 2.5-inch device into a 3.5-inch disk bay.

The SSD itself is black and serious.

The most interesting things are inside, of course. We mean its PCB.

The SandForce controller is surrounded with as many as 32 memory chips which are made by Micron and labeled as 29F64G08CBAAA. However, some batches of this SSD may come with other ONFI 2.2 compliant chips with the same specs. Each of these 25nm flash memory chips has a capacity of 64 gigabits and asynchronous interface. In other words, this is the same memory as in the 120GB model from the same series. Hidden from the user, 16 out of the total 256 gigabytes are used as reserve space. Thus, each controller channel is connected to four flash devices, enabling 4-way interleaving.

By the way, we’re referring to the controller as SandForce SF-2281 but the actual chip is marked as SF-2282. This is no mistake because the latter only differs from the former in packaging and support for 128-bit NAND devices.

The Corsair Force 3 comes with firmware 1.3.3 which is based on SandForce’s reference firmware 3.3.2. The developer says that this firmware version finally solves all the problems with BSODs that plagued the controller for half a year since its release.

Here are the official specs of the 240GB Corsair Force 3:

  • Controller: SandForce SF-2282
  • Interface: SATA 6 Gbit/s
  • Flash memory: asynchronous NAND
  • Capacity: 240 gigabytes
  • Cache memory: n/a
  • Sequential read speed: 550 MB/s
  • Sequential write speed: 520 MB/s
  • Random write speed (in 4KB data blocks): 85,000 IOPS
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