Samsung 850 Pro review: 3D NAND and RAM caching result in the fastest, most durable SSD money can bu
Samsung’s 850 Pro SSD is out on the market and it’s damned impressive. Combine Vertical NAND with the drive’s performance enhancing Rapid Mode, and the 850 Pro destroys all comers.
In the world of SSDs, the Samsung 850 Pro $199.99 is a major achievement. Up until now, all of the advances in SSD technology have come from either shrinking the size of the memory cells through using smaller process nodes, or through packing more data into each cell. For years, that approach won us ever-falling prices and improved performance, but it came with a built-in timer — at each successively smaller process node, it became more and more difficult for manufacturers to ensure NAND would retain its speed and reliability for years.
The alternative to this approach is to adopt 3D NAND, also called V-NAND (Vertical NAND), and stand the entire die stack on its head. The 850 Pro is the first SSD to deploy this method. Samsung has worked on the technology for years. We’ve discussed 3D NAND multiple times before — the basic idea is that by standing the NAND stack on its head and working downwards, it’s possible to build a NAND structure that holds a great deal more data per square millimeter — or at least, that’s the eventual goal.
Right now, the 3D NAND movement is still in its infancy, but Samsung feels the technology is still advanced enough to launch the drive.
When 40nm isn’t 40nm
In the 2D NAND world, Intel and Micron are currently pushing to 16nm, while Samsung stresses that its 3D NAND on 40nm is good enough to keep pace. If true, falling back to 40nm could actually give Samsung some advantages. One of the problems with smaller NAND is that its more prone to data loss and can withstand fewer program/erase cycles.
In theory, Samsung’s 40nm NAND will be far more robust than the 16nm NAND from Intel and Micron. In order to compete on density, Samsung has tilted the die on edge and drilled down, creating a 3D layer stack that, at present, is 32 layers deep. This allows the company to hit (or slightly exceed) the density of cutting-edge NAND flash. In the future, Samsung predicts that it’ll far exceed the density of 2D conventional NAND — all while remaining on the same 40nm process and without the thwack that durability and reliability take as a result.
Because of this, the Samsung 850 Pro has the highest endurance spec on any consumer SSD we’ve ever reviewed (150TB) and easily the longest warranty, at 10 years. Moreover, while there are multiple ways to build 3D NAND, the ITRS expects 3D NAND to rapidly replace 2D planar structures over the next 4-5 years as densities improve and cost scales lower.
Samsung’s Drive Magician
The one other bit we want to mention is the inclusion of Samsung’s Drive Magician. Some of you may remember a few years ago, we reviewed SSD cache drive solutions made by both Intel and software company Nvelo. Not long after, Nvelo was acquired by Samsung, and the company’s drive caching solution makes an appearance with the 850 Pro.
This screenshot is from the 840 EVO, but the interface is identical
Samsung now includes three separate modes for boosting performance of an SSD, including “Maximum Performance,” “Maximum Capacity,” and “Maximum Reliability.” Each item adjusts OS performance and capability to emphasize its selected target — Maximum Capacity disables Hibernation and Automatic Backup, Max Performance sacrifices SSD endurance for higher performance targets, while Maximum Reliability minimizes writes to ensure the drive lasts longer.
Samsung’s Drive Magician also offers RAPID (Real-time Accelerated Processing of I/O Data) mode. In Rapid Mode, the drive reserves a slice of system memory and uses it to cache frequently accessed data and files. Windows Superfetch has done something similar since Windows Vista, but there’s a key distinction — Superfetch only caches reads, while Rapid Mode can cache both reads and writes.
Systems with 8GB of RAM can choose to devote 1GB of memory to the data cache; systems with 16GB can devote up to 4GB of memory. We’ve run through our benchmarks with Rapid Mode enabled and disabled to gauge its impact. Since Rapid Mode does make use of DRAM for caching data, we recommend only enabling it if you have an uninterruptable power supply attached to your primary system. In this case, a few extra minutes of battery life could save you from data loss.