The Samsung SSD 850 120GB Review: A Little TLC for SATA
by Billy Tallis on November 27, 2017 12:00 PM ESTRandom Read Performance
Our first test of random read performance uses very short bursts of operations issued one at a time with no queuing. The drives are given enough idle time between bursts to yield an overall duty cycle of 20%, so thermal throttling is impossible. Each burst consists of a total of 32MB of 4kB random reads, from a 16GB span of the disk. The total data read is 1GB.
The Samsung SSD 850 120GB has a significantly slower random read speed than its predecessors from Samsung, but it is still faster than any other brand. The Micron 3D TLC-based SSDs that are actually currently for sale are the three slowest drives on this test.
Our sustained random read performance is similar to the random read test from our 2015 test suite: queue depths from 1 to 32 are tested, and the average performance and power efficiency across QD1, QD2 and QD4 are reported as the primary scores. Each queue depth is tested for one minute or 32GB of data transferred, whichever is shorter. After each queue depth is tested, the drive is given up to one minute to cool off so that the higher queue depths are unlikely to be affected by accumulated heat build-up. The individual read operations are again 4kB, and cover a 64GB span of the drive.
On the longer random read test that brings in higher queue depths, the rankings are almost unchanged. The 850 120GB is Samsung's slowest, but everyone else is much slower.
At higher queue depths, the Samsung drives scale up to much higher performance levels than the competing 120GB-class SSDs. The 850 is still the slowest of Samsung's drives and it falls short by more than 100MB/s at QD16 and higher, but by that point the 850 is 2.5 times faster than the quickest Micron 3D TLC-based drive.
Random Write Performance
Our test of random write burst performance is structured similarly to the random read burst test, but each burst is only 4MB and the total test length is 128MB. The 4kB random write operations are distributed over a 16GB span of the drive, and the operations are issued one at a time with no queuing.
There aren't huge disparities between the 120GB-class SSDs on the burst random write test, save for the DRAMless HP S700. The Samsung SSD 850 is only slightly slower than the old 850 EVO, but two of the drives using Micron 3D TLC come out on top for this test.
As with the sustained random read test, our sustained 4kB random write test runs for up to one minute or 32GB per queue depth, covering a 64GB span of the drive and giving the drive up to 1 minute of idle time between queue depths to allow for write caches to be flushed and for the drive to cool down.
With a longer test duration that will tend to fill the whatever SLC write cache such a small drive can include, the old Samsung 850 PRO 128GB is unsurprisingly the winner by a wide margin. The Samsung 850 comes in second place and slightly ahead of the old 850 EVO, somewhat corroborating Samsung's claims that their 64L 3D TLC offers improved write performance.
The performance of the Samsung 850 holds up through most of the random write test, but doesn't improve significantly as queue depths grow. By the end of the test, the drive has fallen behind on garbage collection despite the idle time it is allowed between queue depths, and performance drops off. Most of the other drives suffer a similar fate at some point during the test; the 750 EVO is the fastest drive that doesn't show a precipitous drop at any point. The Samsung 850 PRO was still faster than the rest even after its spare area was filled and it was forced to perform garbage collection through the later parts of the test.
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lilmoe - Monday, November 27, 2017 - link
Oh, and so are the Pros... hmmm.Is that a holiday discount or is it that I haven't checked the price in a while?
Arbie - Tuesday, November 28, 2017 - link
Great article, even though its subject is a minor league item. AT quality.bug77 - Tuesday, November 28, 2017 - link
That's the ugly face of SSD: the cheaper they make them, the more we lose durability and access speed...bcronce - Tuesday, November 28, 2017 - link
Still 1000x faster than a mechanical drive, perceptibly as fast as any other SSD for most situations, and will last a lifetime.mapesdhs - Wednesday, November 29, 2017 - link
Definitely will not last a lifetime, and some newer models can have worse steady state performance than a rust spinner.bcronce - Wednesday, November 29, 2017 - link
Even the infamous Samsung 840s were still out-performing 15k SAS drives in their degraded modes. I see free "crackerjack" USB 2.0 flash drives out performing my 7.2k RPM rust buckets.MamiyaOtaru - Thursday, November 30, 2017 - link
no you don'tyifu - Saturday, December 2, 2017 - link
power efficiency test pleaseyifu - Sunday, December 3, 2017 - link
Billy , I would really want to see , is not only the speed , but the power efficiency for a older laptop like my MacBook Pro 13in 2012. if some one really care about speed , they will go for 850 pro 850 EVO, or PCIE. my gaming PC is with 960 pro for windows and 850 evo for storage. my iMac for work is with apple PCIE and a Toshiba HK4R 960GB (power lost protection). SATA speed for a ssd is done.the speed difference between those cheap SSDs are to small.I am thinking to "upgrade" my MacBook Pro mid 2012 from 840 pro to a slower but very very power efficient SSD.
finefunny - Sunday, December 3, 2017 - link
The company has already released several new versions of its OEM models, such as the PM871b, with 64-layer V-NAND. These drives often sell in basic systems from Dell, Lenovo, and other OEM brands. Customers often do not select the components in those systems, so the OEM models fly under the radar.Samsung isn't saying much for now, but it should answer our questions in early 2018. That's when we expect it to roll out new retail SSDs.