– May not be compatible with nVidia controllers Software Package – RAPID can only be enabled for one EVO physical drive, partitions are not supported.
RAPID is a filter driver and requires Magician 4.2.1 or higher and has some limitations. "RAPID IS A FILTER DRIVER AND REQUIRES MAGICIAN 4.2.1 OR HIGHER AND HAS SOME LIMITATIONS." Data are committed at regular intervals to minimize data corruption in case of power loss or system crash. buffers the data into a reserved RAM area and delays the write back to the disk. When applications write to a file, the O.S. The concept behind write caching is to improve performance.
Windows does warn about potential data loss with Write-caching policy. Asked about the potential risk of losing data due to power loss for instance, Samsung stated that it is as safe as the Write Caching policy in Windows, as RAPID complies with the flush buffer command. As such, write I/O performance should see a performance increase with the RAPID enabled. The write cache mostly focuses on small random I/O by collating the data and writes it back in as larger blocks. The blocks with the highest counter stay cached. In this method, each read block is assign a counter, repeated accesses to the block increment the counter. Based on the RAPID description, the caching algorithm used is probably LFU (Least Frequently Used). I see it as an improved version of Windows SuperFetch because it manages not only applications and but also user data. RAPID would only cache the most accessed data blocks, like the last couple of days, instead of loading the whole file into its cache. One good example would be caching a PST file, which is usually large. Which makes sense, since you don’t want to fill the cache with one large file. It keeps track of the hot data based on access, frequency and at the data block level.
The read cache is persistent after reboot, which basically means that it writes a copy of the data map on disk every so often. The cache size is dynamic, 25% of the RAM host capacity up to 1GB, split 50/50 between read and write. The RAPID technology caches reads and writes. To my knowledge, only the EVO line offers host SDRAM caching for SSDs. It is result of a joint collaboration between Samsung and NVELO, now a subsidiary of Samsung since December 2012. RAPID is the fancy acronym for Real Time Accelerated Processing of I/O Data. Sandisk’s Extreme II uses a similar technology, called nCache, although the reserved area is smaller, around 1GB.
I will assume that, based on a SLC buffer size of 3GB, I will mostly see SLC write performance. Based on my personal computer usage pattern, my host writes about 10GB/day. The buffer is flushed when the drive is idle. After that it drops back to TLC speed until the data is transferred to the TLC nand. Here is how it works, as long as the buffer is not full, the writes performs at SLC speed. The table below shows the reserved amount depending on the drive size. That reserved amount is used as emulated SLC, which results in faster write I/O.
Samsung converted the space normally used for overprovisioning in the first generation of the 840 into a write buffer area. TurboWrite: This is the technology at the core of the write I/O improvement. "TURBOWRITE: THIS IS THE TECHNOLOGY AT THE CORE OF THE WRITE I/O IMPROVEMENT" New controller, EMX: The fifth generation is still a triple-core ARM cortex R4 but is clocked at 400Mhz, a 100Mhz bump or a 33% performance increase. SATA 3.1 support: Among the improvements in the SATA 3.1, Queued TRIM Command is the most relevant to SSDs. The 128Gb TLC NAND opened up access to larger capacity, up to 1TB. Let’s check the specifications then I will dive into the review with the Amazon “SSD best seller”, the EVO 250GB and the EVO 750GB. It shows that performance is not solely based on NAND architecture but other components are almost equally important. Looking at the data-sheets from Samsung for the 840 EVO, it appeared that Samsung has closed the gap between MLC and TLC. The first generation of Samsung TLC SSD stacked up with MLC drives on the read I/O but lagged behind in term of writes I/O. With this new line, Samsung broadens their offer with five drives ranging from 120GB up to 1TB. Capitalizing on their success with the 840 series, Samsung released their new SSD TLC based drives named EVO.