Data Type Comparison & TLC Sequential Write Speed
Samsung's architecture doesn't discriminate between compressible and incompressible data. Both data types move to and from the flash at full speed. We rarely mention this unless one data type enjoys higher performance than the other. But we want to bring it up this time because we expect another 2TB SSD to hit the market soon, which will be biased to one data type.
In our Computex coverage of TLC-based products, we talked about the need to hide TLC's low write speeds. All of the products we've tested with triple-level-cell flash utilize some form of emulated SLC write cache that yields better performance in short bursts, but quickly falls back to native TLC write speeds once the buffer fills. In some cases, that means sequential write performance as low as 125 MB/s.
Most of the time you'll never see rates that low since the cache is deliberately large enough to soak up the writes. That changes when transferring large files like big movies, though.
Samsung does an excellent job masking the native TLC performance with its 850 EVO. We had to really work to build a write test that'd shed more light on the sequential write performance of TLC. The 850 EVO 2TB has so much emulated SLC from TurboWrite that even a 42GB Blu-ray image transfer doesn't slow down.
