Review: SanDisk Extreme SSD with On-The-Fly Compression

Published: February 25, 2013 9:00 AM
By Vincent Alzieu
Translated by: Catherine Barraclough
Extreme by name, extreme by nature—this 240 GB SanDisk solid state drive promises speedy data transfer rates of 550 MBps in read mode and 520 MBps in write mode. It's quite surprising to see these kinds of speeds in an SSD at this relatively modest price point.

The truth about those super-fast data transfer speeds is that they're measured in the best possible conditions for this particular SSD, which happens to compress data on the fly. This brings two main advantages. First, compressing data means less writing, so the job gets done quicker. Second, the MLC memory cells are used less, which extends their lifespan.

Ssd sandisk


With on-the-fly compression, it's no surprise to find a Sandforce controller in this SSD—an SF-2281 SATA 6 Gbps controller, to be precise. The good news is that this onboard compression function really helps extend the disk's lifespan (if that's even necessary—see below). This particular model was put through its paces for several weeks in a real-life set-up, and we found that the quantity of data written to the memory was 20% lower than that requested by Windows. The opposite would be true for an SSD with no compression mode, as solid state drives write units that are bigger than the actual amount of data being stored.
Sandisk 240 go ssd extreme 1354606369

Unlike most consumer tech products, this SanDisk SSD comes with a three-year warranty. This is no doubt aimed at reassuring the buying public, as SSDs seem to have developed a bad reputation for reliability. To be honest, this reputation isn't really warranted, as it's partly linked to teething troubles with the technology when it first arrived on the market. To some extent it also stems from reliability issues with certain specific series of SSDs, which firmware updates have since put right. Anyway, SanDisk is promising 1.4 to 2.5 million hours of mean time before failure (MTBF) for this 240 GB Extreme SSD. That means that even if you use it every day for 24 hours a day, this SSD would apparently still last for 353 years?!? Hmm ... maybe SanDisk would be better off sticking to more believable realistic values here. And maybe all SSD-makers could one day agree on a standard way of estimating drive lifespan.

In terms that are a bit more down-to-earth, MLC memory—as used here—is usually expected to have a lifespan of around 3000 write cycles per cell. That already makes for an estimated lifespan of 100 years of intensive use (20 GB of data written and erased every day on the SSD, which is huge—an average person doing office-style computing for eight hours per day would only clock up a maximum of 10 GB per day).

This SSD is 9 mm thick and weighs 79 grammes, which is within average. Still, the lightest models from Samsung, for example, weigh nearer 50 grammes, which can make all the difference in a laptop.

Data Transfer Speeds

data transfer speeds

File transfer (photos, videos, etc.): sequential data transfer rates

In benchmark tests, we measured read speeds of around 500 MBps with this SSD, compared with 400 MBps in our practical tests using video, photo, audio files and one big ISO file (none of which can be compressed that much—not as much as the files used in our benchmark tests in any case). The data transfer rate therefore drops a bit (by about 10%) but is still very high.

In write mode, the benchmarks show speeds of 460 MBps whereas our practical tests gave 360 MBps. Performance-wise, the SanDisk Extreme therefore falls mid-way between the Samsung 840 and 840 Pro, but with a price tag that's closer to that of the standard 840. Nice!

With a 514 MBps sequential data transfer rate measured with large files, this SanDisk SSD offers the same sequential read speeds as the top-notch Samsung 840 Pro—the best of all consumer-level SSDs on the market right now. In fact, it's flirting with the limits of the SATA III interface, which is theoretically capped at 600 MBps.

Sequential write speeds are obviously a little slower. We measured 253 MBps, which is a good score, but it's a fair way behind the exceptional 400 MBps seen in the 840 Pro.

Accessing programs: 4K random access time

Random access speeds are fast here. In fact, they're comparable with those of the Samsung 840 Pro, with a random access read speed measured at 33 MBps with 4 KB files. The 4K random access write speed was measured at 64 MBps.
4/5 SanDisk 240 GB Extreme Solid State Drive DigitalVersus 2013-02-25 10:00:00


  • Three-year warranty
  • MLC memory
  • Effective on-the-fly compression = boosted SSD lifespan
  • Fast read and write speeds


  • Not as fast as the Samsung 840 Pro
  • Not as light as the 840 Pro (30 g can make all the difference in a laptop!)


The SanDisk 240 GB Extreme is an excellent value SSD in terms of quality, lifespan and price. This SSD ensures fast data transfer speeds—they're not the best, but they're on the better side of average—as well as on-the-fly data compression which saves on memory and extends the drive's lifespan.