Do Samsung’s mainstream SSDs fare as
well as its professional drives?
The SSD 840 Evo range is the only one
on test to use TLC NAND, which stores 3-bits per cell. Specifically, it’s
Samsung’s 19nm Toggle 2 NAND. The increased density compared to MLC NAND
decreases cost, hence the drives’ attractive prices, but it typically lowers
performance and endurance too.
Samsung SSD 840
Nevertheless, Samsung has a few tricks
up its sleeve. The MEX controller, for example, is Samsung’s latest and
greatest, using the same three ARM cores used in the SSD 840 Pro’s MDX
controller, but running at 400MHz (100MHz faster). It’s supported by Samsung’s
LPDDR2-1066 cache – 512MB in the lower capacities and 1GB in the 1TB model.
Samsung SSD 840 EVO 250GB $206.51 inc
VAT
To combat slow TLC write speeds, the
Evo drives use TurboWrite. This treats a portion of the NAND as SLC memory,
which is much faster. The size of the portion used increases with capacity –
3GB, 6GB and 12GB in these three drives. If a write process exceeds this
buffer, performance will drop to normal TLC levels.
Another trick is RAPID Mode, enabled
through the excellent Magician software. It utilises system RAM and resources
for caching and buffering to offer potentially massive performance gains,
although results depend on the workload. All the drives also ship with a
typical three-year warranty, although some drives offer five years.
The Evo’s sequential reads aren’t top
of the pack, but we saw 512-518MB/sec in AS SSD and 534-541MB/sec in
CrystalDiskMark, so there’s little to be concerned about. Sequential writes are
fantastic, though, and TurboWrite’s impact is obvious. The Evo drives secure
the top three spots in AS SSD, and beat the competing similar-capacity Vector
150 drives in CrystalDiskMark too.
For random reads, it’s an outstanding
victory for the Evos, with the faster controller giving them the edge over the
more expensive Pro drives. They take first, second and third place in both
tests, and they’re the only drives to hit over 40MB/sec. Random writes,
meanwhile, are on a par with the 840 Pro series.
The 64-queue-depth random reads in AS
SSD aren’t great, especially for the 250GB drive, but 32-queue-depth
performance in CrystalDiskMark is much better, with the 1TB drive coming second
overall with 405.9MB/ sec, and the 250GB not far behind with 401.1MB/sec.
Such queue-depths are mostly
unrealistic for the Evo’s intended audience, but even so, the 1TB and 500GB
drives are strong performers for high queue-depth writes, losing only to the
Vector 150s. The 250GB drive, meanwhile, falls down the charts, probably
suffering from having less NAND dies per channel.
Performance is also good in PCMark 7,
although they can’t match the 840 Pro drives here. We saw 110-114MB/sec in the
application start test, with Plextor and Toshiba both ahead. Tasty speeds of
146-151MB/sec in the gaming test are enough to surpass Plextor and pull level
with the Toshiba Q Series, however.
The BootRacer results are nothing too
impressive though – the 1TB drive has the slowest boot time, but higher
capacitive drives typically suffer in this respect. Iometer is the Evo’s
weakest point, although again, such workloads are irrelevant to the vast
majority of consumers. The 1TB drive manages a respectable 32,986 IOPS, but the
250GB achieved just 22,621 IOPS. In this case, the relentless writes would have
quickly surpassed the drive’s TurboWrite buffer and passed into the slow TLC
NAND.
Conclusion
The SSD 840 Evo drives have their
limits, but for the majority of home PC users, including hardware enthusiasts,
they’re fantastic all-rounders. The Samsung SSD 840 Evo 250GB comes out a
little slower and more expensive than its bigger siblings, but equally, its
price of 54p per gigabyte is still very reasonable, making it one of the best
drives available at this popular capacity.
Verdict
Fast, attractively priced and backed
by great software, the Evo range is a deserving winner of this month’s Labs.
