Sequential Performance – HDTach, HDTune, File Copy, YAPT (sequential)
We have shifted over to combining our results into two groupings for consumer reviews. First up is 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.
Samsung 850's have always turned in superb QD=1 sequentials. The write speeds reflect more of the TLC write speeds, as this is a 'full span' test, and the SLC buffers are quickly exhausted. Of note is how the 120GB models match the 2.5" EVO, despite their much smaller packaging.
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.
All of the new models behave exactly like their 2.5" counterparts here. No surprises.
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.
Despite being TLC units, the 500GB and 1TB capacities easily compete directly against MLC drives like the Crucial MX100 and Intel SSD 730. The 120GB capacity is more limited by a reduced die count and held back in bulk file creation by a ~150 MB/sec TLC write speed maximum.
Performance results in the file copy test were good, with the expected longer copy times for the 120GB models. Note that while we don't have a direct comparison in this test, these speeds are also on par with IMFT-driven MLC SSDs at the same (120/128GB) capacity point.
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.
YAPT is a short enough workload that it can be cached by Samsung's TurboWrite tech, even in the 3GB SLC cache of the 120GB model. The end result is speeds pegged at SATA 6Gb/s throughputs, regardless of capacity.