The sequential read/write scores are almost equivalent to the top speed of your car on a straight road ( NOTE: This is no longer true as a single-threaded sequential read/write won't achieve the "top" speed with recent NVMe SSD devices). 1092006274Ī: AJA System Test Lite also only runs sequential 5408 KiB block (default) read/write tests. This is one of the reasons why CDM and ADM have the multi-threaded sequential read/write measurements. With NVMe SSD devices, a single-threaded sequential read/write typically cannot achieve the best performance of the device. If you are only interested in a particular scenario (the data transfer rate your storage device/controller/interface can achieve from a single-threaded sequential read/write), there is nothing wrong with Blackmagic Disk Speed Test. d425264550Ī: Blackmagic Disk Speed Test only runs sequential 5400 KiB (0x546000 bytes = 5529600 bytes = 5400 x 1024 bytes) block read/write tests. Q: How about Blackmagic Disk Speed Test?. This doesn't necessarily make sense but ADM uses the same logarithmic scale as CDM in order to make the results images comparable. Q: The score result green bar is not a linear scale?Ī: It uses a logarithmic scale. You could always change the settings to 5 runs with 1GiB file size if you want the test settings to be identical to CDM5. Also I noticed that the random write score on SSD gets significantly higher on subsequent runs which are possibly benefiting from the erase cycle completed from the previous runs. So I decided to set it to 500MiB by default. I chose the file size 500MiB because random read/write tests on a hard drive would take somewhat impractically long time (more than ten minutes) with 1GiB. And ADM shows the median score when there were multiple runs. Why?Ī: CDM5 uses 5 runs with 1GiB file size, and shows the highest score. Q: CDM5 and ADM have different default test settings. And it shouldn't really matter where the read/write requests are coming from.
Long answer: I was going to try to mimic as close as possible but I couldn't find a good way to queue multiple asynchronous read/write requests "without" using multiple threads. Why?Ī: Short answer: Q1T32 on CDM5 is equivalent to QD32 on ADM. I could change the maximum queue depth to up to about 2,000 but 1,024 should be good enough for now.Ĭode: Select all $ sysctl kern.num_taskthreads Q: Why is the queue depth is limited to up to 1,024?Ī: macOS only allows up to 2,048 threads per process as of this writing.
Seq QD: Reading/writing one big file sequentially from multiple apps.But it should give you similar results.Ī: Four different tests represent different storage usages. And it may give you slightly different test results. ADM (AmorphousDiskMark) uses a different storage test engine I wrote. It has its own way of measuring the read/write performance with options that CDM5 specifies.
CDM5 (CrystalDiskMark 5) uses Microsoft DiskSpd test engine. Q: Are the test results compatible with CrystalDiskMark 5?Ī: Not exactly. I will replace it with something nicer at some point.
#Understanding blackmagic disk speed test results mac#
Q: Is there a Mac App Store version of AmorphousDiskMark?Ī: I wish I could draw, paint, design app icons, and more.
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