This software cache is also used to "optimize" host writes before they hit the SSD.
When enabled, RAPID mode allocates up to 1GB of system memory to storing frequently accessed data. Dubbed RAPID mode, this scheme uses system DRAM to accelerate system performance. The 840 EVO has a second layer of caching enabled by Samsung’s SSD Magician software. The 120 and 250GB models can cache up to 3GB of data, while the higher-capacity models have even larger buffers. The size of the write cache varies depending on the drive’s capacity. Cached writes are only moved to main storage during idle time, though host writes may be sent directly to main storage if the TurboWrite buffer is full. The Samsung implementation is a pure write buffer it caches all incoming host writes regardless of whether they’re sequential or random. TurboWrite sounds similar to the nCache scheme employed by SanDisk’s Extreme II SSD, but there are a few key differences. The single-bit flash offers higher write performance than TLC memory, but it has only one third the storage capacity per cell. However, the portion dedicated to TurboWrite is addressed as one-bit SLC NAND. Most of the EVO’s flash memory is configured as TLC NAND with three bits per cell. The boost in write speeds is made possible by a feature called TurboWrite technology, which is essentially a high-speed write cache built into the NAND. Improved write performance is one of the EVO’s defining characteristics. In the meantime, we can share a few interesting tidbits about the EVO and its unique approach to caching.
Fancycache review full#
We’ve since learned much more about the drive, and we’ll have a full review soon. The initial press release covered the basics, but it was a little short on the nerdy details we tend to obsess over here at TR. Samsung just announced its 840 EVO solid-state drive.