The drives are given enough idle time between bursts to yield an overall duty cycle of 20%, so thermal throttling is impossible. Our first test of random read performance uses very short bursts of operations issued one at a time with no queuing. The only attempt to tune the machines for performance was changing two sysctls to allow more threads to be used to handle asynchronous IO-necessary for testing higher queue depths, but not needed for real-world low queue depth workloads. These tests were run on two different MacBook Pro systems: a base model 13' Retina MacBook Pro from 2015 with a dual-core Broadwell processor, and a high-end 15' Retina MacBook Pro (Late 2013 model) with a quad-core Haswell processor.

However, with the overhead of a copy-on-write filesystem and background traffic from the OS getting in the way, and with an entirely different host operating system, the numbers below are not at all comparable to our previous results on our standard desktop testbed.

The amount of data read or written by each test is the same as for our usual Linux-based synthetic benchmark results. A clean install of MacOS 10.14 Mojave was used on each drive, and instead of having the tests access the drive as a raw block device, the tests were run against ordinary files residing on the same APFS filesystem as macOS and the testing software. Instead of running the OS off a separate drive, the drives under test were used as the only storage attached to the system. Without our ATSB tests to give a more real-world picture to counterbalance the idealized synthetic benchmark results, we chose to reconfigure the synthetic tests to use a somewhat more realistic configuration. This is the best way to measure a drive's raw performance capability without any interference and minimal overhead, but that's not usually a very realistic configuration. Our usual configuration for these tests has the drive under test as a secondary drive, with nothing on the drive other than the data written by the test itself. However, our suite of synthetic benchmarks uses the cross-platform FIO tool, so these tests could be easily adapted to run under macOS. Our AnandTech Storage Bench trace-based tests are Windows-only, and running them on a Mac in a Boot Camp configuration wouldn't give us much insight beyond running the same ATSB tests on our usual desktop testbed.

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