The Samsung 750 EVO (120GB & 250GB) SSD Review: A Return To Planar NAND

Performance Consistency

Our performance consistency test explores the extent to which a drive can reliably sustain performance during a long-duration random write test. Specifications for consumer drives typically list peak performance numbers only attainable in ideal conditions. The performance in a worst-case scenario can be drastically different as over the course of a long test drives can run out of spare area, have to start performing garbage collection, and sometimes even reach power or thermal limits.

In addition to an overall decline in performance, a long test can show patterns in how performance varies on shorter timescales. Some drives will exhibit very little variance in performance from second to second, while others will show massive drops in performance during each garbage collection cycle but otherwise maintain good performance, and others show constantly wide variance. If a drive periodically slows to hard drive levels of performance, it may feel slow to use even if its overall average performance is very high.

To maximally stress the drive's controller and force it to perform garbage collection and wear leveling, this test conducts 4kB random writes with a queue depth of 32. The drive is filled before the start of the test, and the test duration is one hour. Any spare area will be exhausted early in the test and by the end of the hour even the largest drives with the most overprovisioning will have reached a steady state. We use the last 400 seconds of the test to score the drive both on steady-state average writes per second and on its performance divided by the standard deviation.

Starting with a look at steady-state performance, the 750 EVO is clearly inferior to the 850 EVO, particularly at 250GB. But it outperforms most of the planar TLC competition and the occasional low-end MLC drive.

The high consistency score is a hallmark of Samsung's top-notch controller architecture. The 750 EVO is in an entirely different league from the planar TLC drives.

Default	Samsung 750 EVO 120GBSamsung 750 EVO 250GBADATA Premier SP550 120GBADATA Premier SP550 240GBCrucial BX100 250GBCrucial MX200 250GBOCZ ARC 100 240GBOCZ Trion 150 240GBOCZ Vector 180 240GBPNY CS1311 120GBPNY CS1311 240GBPNY CS2211 240GBPlextor M6V 256GBSamsung 850 EVO 120GBSamsung 850 EVO 250GBSamsung 850 Pro 128GBSamsung 850 Pro 256GBSanDisk Ultra II 240GBOCZ Trion 100 240GB
25% Over-Provisioning	Samsung 750 EVO 120GBSamsung 750 EVO 250GBADATA Premier SP550 120GBADATA Premier SP550 240GBCrucial BX100 250GBOCZ ARC 100 240GBOCZ Trion 100 240GBOCZ Trion 150 240GBOCZ Vector 180 240GBPNY CS1311 120GBPNY CS1311 240GBPNY CS2211 240GBPlextor M6V 256GBSamsung 850 EVO 120GBSamsung 850 EVO 250GBSamsung 850 Pro 128GBSamsung 850 Pro 256GBOCZ ARC 100 240GBOCZ Trion 100 240GBSanDisk Ultra II 240GB

The 750 EVO's initial burst of high performance is relatively short-lived, but it transitions into a very well-regulated steady state. The gradual performance recovery before a second smaller drop in performance is less pronounced than on the other Samsung drives, but is still present.

With extra overprovisioning, the 750 EVO's steady state shows much looser performance regulation but is still delivering a better worst-case than its competition's best-case.

Default	Samsung 750 EVO 120GBSamsung 750 EVO 250GBADATA Premier SP550 120GBADATA Premier SP550 240GBCrucial BX100 250GBCrucial MX200 250GBOCZ ARC 100 240GBOCZ Trion 150 240GBOCZ Vector 180 240GBPNY CS1311 120GBPNY CS1311 240GBPNY CS2211 240GBPlextor M6V 256GBSamsung 850 EVO 120GBSamsung 850 EVO 250GBSamsung 850 Pro 128GBSamsung 850 Pro 256GBSanDisk Ultra II 240GBOCZ Trion 100 240GB
25% Over-Provisioning	Samsung 750 EVO 120GBSamsung 750 EVO 250GBADATA Premier SP550 120GBADATA Premier SP550 240GBCrucial BX100 250GBOCZ ARC 100 240GBOCZ Trion 100 240GBOCZ Trion 150 240GBOCZ Vector 180 240GBPNY CS1311 120GBPNY CS1311 240GBPNY CS2211 240GBPlextor M6V 256GBSamsung 850 EVO 120GBSamsung 850 EVO 250GBSamsung 850 Pro 128GBSamsung 850 Pro 256GBOCZ ARC 100 240GBOCZ Trion 100 240GBSanDisk Ultra II 240GB

A closer look at the 750 EVO's steady state is pretty boring, with no clear patterns of periodic background maintenance or sporadic outliers.