File Copy Speed
We use AS SSD version 1.7.4739.38088 to benchmark the speed of copying different types of files within a single partition the size of the whole SSD. The SSDs are tested in their steady state again.
Copying files within the same SSD is a specific load which requires high speed of processing both read and write requests simultaneously. The Samsung 840 EVO doesn’t perform consistently here. Its speed depends on the type of data and, obviously, on whether the copied files can fit into the TurboWrite cache.
RAPID Software Cache
In our tests of the Samsung 840 Pro and Samsung 840 we noted that they came with Samsung Magician, one of the best SSD management utilities available. It has a user-friendly interface and a lot of features from viewing SMART information and updating firmware to Secure Erase, an in-built performance benchmark and an OS optimizer. The utility has been updated for the Samsung 840 EVO and now supports the exclusive RAPID technology.
RAPID (Real-time Accelerated Processing of IO-Data) implements an additional level of caching in the OS. With RAPID enabled, the Magician tool creates a cache buffer in system memory to accelerate read and write operations. This functionality is based on solutions from NVELO, which has recently been bought by Samsung. NVELO is known among enthusiasts for its optimizations of hybrid disk subsystems consisting of an SSD and an HDD. Now this technology has been adapted for using with an SSD and system memory.
Currently RAPID is supported by Samsung’s 840 EVO and 840 Pro drives. Although it is a software technology, it cannot be enabled for other SSDs. RAPID requires at least 2 gigabytes of system memory and Windows 7 or 8. You enable it by simply clicking a button in the Magician interface.
After rebooting, a 1GB cache is created in system memory to store low-level read/write disk requests to the Samsung drive, improving the latter’s performance. According to the synthetic benchmark CrystalDiskMark, the Samsung 840 EVO gets as fast as PCIe drives when you enable RAPID:
It must be noted that RAPID can only accelerate reading when the same data is accessed repeatedly, so it can be taken from the cache. That’s why real-life applications may not show such a high performance boost. The performance benefits we’ve got with our configuration in PCMark 8 after enabling RAPID are illustrated by the following table:
As you can see, the RAPID effect varies greatly between applications. It is low in games but huge in Photoshop. The average performance growth is an impressive 55%.
Despite the substantial performance benefits from RAPID, many users don’t like such software technologies since they lower the robustness of the file system. If the computer fails while the RAM cache contains data which is not yet written to the SSD, the data may get lost and the entire file system may get damaged.
Samsung says that such problems are very unlikely as the RAPID technology tries to keep data in the RAM cache for as little time as possible. Instead of quickly processing write requests by placing them in the cache, the point is in combining random-address requests with a short request queue into long-queue requests.
RAPID takes a rational approach to system resources. The system memory employed for disk requests is freed up when requested by other OS processes. The technology itself may temporarily switch off when the CPU load is high.