Sequential Performance – HDTach, HDTune, File Copy, YAPT (sequential)
We are trying something different here. Folks tend to not like to click through pages and pages of benchmarks, so I'm going to weed out those that show little to no delta across different units (PCMark). I'm also going to group results by performance trait tested. We'll start with sequential performance:
HD Tach will test the sequential read, random access and interface burst speeds of your attached storage device (hard drive, flash drive, removable drive, etc). All drive technologies such as SCSI, IDE/ATA, 1394, USB, SATA and RAID are supported. HDTach tests sequential performance by issuing reads in a manner that was optimized more for HDD access, but this unique method has proven useful in evaluating the sequential response time of SSDs. The accesses are relatively small in size (2k), and are issued with a single working thread (QD=1). The end result is that devices with relatively IO high latency will not reach their ultimate rated speed.
Sequentials come out looking fairly solid. The 120GB 850 EVO runs out of cache fairly quickly, so it's average write is closer to its rated TLC speed of 150 MB/sec. The 500GB model has no problem performing equivalent to a 256GB 850 Pro.
HDTune tests a similar level of features as compared with HDTach, but with a different access pattern. Thus provides us with an additional set of benchmark numbers to compare between storage configurations. CPU utilization has proven negligible with modern processing horsepower, and is no longer included. Additionally, we do not include write performance due to HDTune's write access pattern not playing nicely with most SSDs we have tested it on.
Reads are pegged even for the smallest capacity 850 EVO, but note the performance optimizations keeping things a bit more consistent than the older 840 EVO.
PCPer File Copy Test
Our custom PCPer-FC test does some fairly simple file creation and copy routines in order to test the storage system for speed. The script creates a set of files of varying sizes, times the creation process, then copies the same files to another partition on the same hard drive and times the copy process. There are four file sizes that we used to try and find any strong or weak points in the hardware: 10 files @ 1000 MB each, 100 files @ 100 MB each, 500 files @ 10 MB each and 1000 files at 1 MB each.
The 850 EVO 120GB is the slowest here, but you should note that it will still be on par with competing 128GB units using IMFT flash (typically limited to the same 150MB/sec write speed).
File copies uses the standard Windows copy, and the added threading of this operation lets the SSDs more heavily use their respective firmware optimizations. The 500GB 850 EVO is keeping a great pace here, obviously not needing to use its TurboWrite cache to keep up with the 850 Pro, and handily trounce the other comps. The 120GB EVO also closes in with the rest of the pack, even despite its slower write speed.
YAPT (yet another performance test) is a benchmark recommended by a pair of drive manufacturers and was incredibly difficult to locate as it hasn't been updated or used in quite some time. That doesn't make it irrelevant by any means though, as the benchmark is quite useful. It creates a test file of about 100 MB in size and runs both random and sequential read and write tests with it while changing the data I/O size in the process. The misaligned nature of this test exposes the read-modify-write performance of SSDs and Advanced Format HDDs.
Despite its age, YAPT is able to give is fairly accurate throughput figures for multi-GB/sec transfers. YAPT is a short enough run that it is cached in even the smallest 850 EVO's TurboWrite cache, so it's no surprise that the new models squeeze themselves into the tight band at the top of the charts.