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The first consumer SSD with 3D NAND
Despite the complexity of its underlying flash, the 850 Pro is relatively straightforward. It's a direct replacement for Samsung's previous desktop flagship, the 840 Pro, which has been around since 2012. That drive had a good run, but it lacks a few key features and tops out at 512GB. The 850 Pro goes all the way up to a terabyte, and it has all the perks one might expect from a modern SSD.

Although the case conforms to the 2.5" form factor, the diminutive circuit board looks more like a 1.8" drive. Our 512GB sample has four flash packages on the back, plus four more on the top. The other side of the board also houses the controller chip and its accompanying DRAM. Like the flash, these components are manufactured by Samsung. Precious few SSD makers can match the firm's level of vertical integration.

The 850 Pro has a Samsung MEX controller with eight parallel NAND channels and a 6Gbps Serial ATA interface. That configuration is pretty typical for consumer SSDs, and the MEX chip is especially familiar. Samsung's value-oriented 840 EVO uses the same chip. The controller has three ARM-based cores, just like the MDX chip behind the 840 Pro, but Samsung claims there's more "hardware automation" built in. The clock frequency is higher, as well. While the MDX is clocked at 300MHz, the MEX runs at 400MHz—or it does in the EVO, anyway. We're still waiting for specifics on the 850 Pro's controller frequency.

Whatever the clock speed, the frequency is likely dynamic to some degree. The 850 Pro has a thermal throttling mechanism that dials back performance if the temperature gets too high. Overheating shouldn't be a problem in desktops, but it could be an issue in mobile systems.

In another nod to notebooks, the 850 Pro supports the ultra-low-power DevSleep mode defined by the SATA spec. Samsung claims the drive's 2-mW DevSleep draw is lower than that of any other 2.5" SSD. The 840 Pro draws over 10 mW while slumbering, the company says.

Hardware-based encryption is also on the menu. The 850 Pro can scramble data with a 256-bit AES algorithm, and it supports the requisite Windows eDrive (IEEE 1667) and TCG Opal 2.0 standards.

Capacity Max sequential (MB/s) Max 4KB random (IOps) Price $/GB
Read Write Read Write
128GB 550 470 100,000 90,000 $129.99 $1.02
256GB 550 520 100,000 90,000 $199.99 $0.78
512GB 550 520 100,000 90,000 $399.99 $0.78
1TB 550 520 100,000 90,000 $699.99 $0.68

The family hits the most popular capacity points between 128GB and 1TB. Surprisingly, the base model's performance ratings are almost identical to those of its bigger brothers. Lower-capacity SSDs are typically slower because they lack sufficient NAND dies to exploit the controller's internal parallelism. Samsung says V-NAND is fast enough to make up the difference, allowing the 128GB drive to largely match its siblings. According to the official specs, the 128GB unit only lags behind in sequential writes—and by only about 10%.

If V-NAND helps the lower-capacity drives keep up, it should theoretically make the higher-capacity ones even faster. The 850 Pro's performance appears to be bound by the Serial ATA interface, though. A faster PCI Express interface will likely be required to fully exploit V-NAND's potential. That said, Samsung claims the 850 Pro still offers a speed boost at the lower queue depths associated with typical client workloads. Performance consistency is supposed to be improved, as well. We'll see how the drive stacks up against a wide range of competitors in a moment.

First, we should discuss endurance, which we haven't had the time to test ourselves. The 850 Pro has the highest endurance spec we've encountered on a consumer SSD: 150TB of total writes, or 80GB per day over five years. That's a big step up from the 840 Pro, which is rated for only 73TB of total writes, but don't read too much into those numbers. Our ongoing SSD Endurance Experiment has demonstrated that modern drives can take a lot more than their specifications suggest. All six of our subjects, including the 840 Pro and Samsung's TLC-based 840 Series, wrote hundreds of terabytes without issue. The 840 Pro has written over 1.1 petabytes to date, and it's still going strong.

Most users will struggle to write more than 150TB during the 850 Pro's useful life, making its class-leading endurance rating somewhat academic. The 10-year warranty is in the same boat. While I admire Samsung's willingness to stand behind the product for that long, the Serial ATA interface will probably be scarce a decade from now. By then, even a terabyte SSD may be too small to be useful.

At least the longer warranty and higher endurance rating help to offset the sticker shock. The 850 Pro is one of the most expensive consumer SSDs around, with per-gigabyte prices ranging from $0.68-$1.02. It's possible street prices could end up being lower than Samsung's MSRPs, but the 840 Pro maintained similar pricing for most of its life. I wouldn't expect its successor to participate in a price war anytime soon. Samsung can race to the bottom with its value-oriented 840 EVO SSD.

The 850 Pro has a couple of other extras worth mentioning. Data migration software is included for folks upgrading existing systems. Then there's Samsung's Magician utility, which covers firmware updates, health monitoring, and OS optimization, among other functions. The utility can even allocate a portion of user-accessible storage as additional overprovisioned area.

The Magician app also serves as a gateway to RAPID mode, otherwise known as Real-time Accelerated Processing of I/O Data. Disabled by default, this optional caching scheme commandeers a slice of system memory to serve as a repository for frequently accessed data. Windows' SuperFetch mechanism behaves similarly, but it's limited to caching application data to speed read requests. RAPID covers all data types and even incoming writes. It only discriminates against larger media files that won't benefit from quicker access times.

Caching writes in volatile DRAM is risky, but RAPID mode moves those writes to the SSD whenever the Windows write cache is flushed, so the chance of data loss should be relatively low. The cache's contents are written to the drive when Windows shuts down, and they're loaded back into RAM when the OS boots up. There's no need to re-train the system after a reboot.

RAPID mode debuted alongside the 840 EVO before migrating to the 840 Pro. The cache size has been capped at 1GB, but the latest revision introduces a 4GB option for systems with 16GB of RAM. Our test rigs have 8GB of RAM, so we had to make do with a 1GB cache. We've tested the 850 Pro with and without RAPID mode enabled to gauge its performance impact. Speaking of which, let's move on to the benchmark results on the next page.