The Samsung SSD 850 120GB Review: A Little TLC for SATA

Sequential Read Performance

Our first test of sequential read performance uses short bursts of 128MB, issued as 128kB operations with no queuing. The test averages performance across eight bursts for a total of 1GB of data transferred from a drive containing 16GB of data. Between each burst the drive is given enough idle time to keep the overall duty cycle at 20%.

The burst sequential read performance of the Samsung SSD 850 120GB places it in the second tier of 120GB-class drives, but it's actually the fastest of the current models. The performance is a clear improvement over the 850 EVO but is about the same as the 750 EVO and the HP S700.

Our test of sustained sequential reads uses queue depths from 1 to 32, with the performance and power scores computed as the average of QD1, QD2 and QD4. Each queue depth is tested for up to one minute or 32GB transferred, from a drive containing 64GB of data.

On the longer test of sequential reads, the Samsung 850 falls well below the standard set by Samsung's earlier drives and ends up slightly slower than the HP S700. The S700 Pro and ADATA SU800 are in last place with less than half the performance of the 850 120GB.

Samsung SSD 850 120GBADATA Premier SP550 120GBADATA Ultimate SU800 128GBADATA XPG SX930 120GBHP S700 120GBHP S700 Pro 128GBPNY CS1311 120GBSamsung 750 EVO 120GBSamsung 850 PRO 128GBSamsung 850 EVO 120GB

Most drives show no performance scaling with queue depth on the sequential read test. The older Samsung drives all show some improvement from QD1 to QD2 and are steady after that, while the 850 120GB is simply the same speed across the board.

Sequential Write Performance

Our test of sequential write burst performance is structured identically to the sequential read burst performance test save for the direction of the data transfer. Each burst writes 128MB as 128kB operations issued at QD1, for a total of 1GB of data written to a drive containing 16GB of data.

The short burst sequential write speed of the Samsung SSD 850 120GB is comparable to Samsung's other drives in this capacity class, and is better than any other current drive for this segment.

Our test of sustained sequential writes is structured identically to our sustained sequential read test, save for the direction of the data transfers. Queue depths range from 1 to 32 and each queue depth is tested for up to one minute or 32GB, followed by up to one minute of idle time for the drive to cool off and perform garbage collection. The test is confined to a 64GB span of the drive.

On the longer sequential write test, the Samsung SSD 850 120GB is tied for second place, though the performance of the 850 PRO far outshines everything else.

Samsung SSD 850 120GBADATA Premier SP550 120GBADATA Ultimate SU800 128GBADATA XPG SX930 120GBHP S700 120GBHP S700 Pro 128GBPNY CS1311 120GBSamsung 750 EVO 120GBSamsung 850 PRO 128GBSamsung 850 EVO 120GB

As with sequential reads, most of these drives handle sequential writes at the same speed regardless of queue depth. The 850 PRO is the only one to show substantial improvement as queue depths increase. Several other drives experience temporary hits to their write performance as a result of their SLC write caches filling and forcing the drive to perform garbage collection, but most are steady through most of the test.