AmorphousDiskMark

AmorphousDiskMark

A macOS storage benchmark tool that measures read/write performance in MB/s and IOPS. Inspired by CrystalDiskMark for Windows.

Features

• Sequential benchmarks: 1 MiB block reads/writes, single-queue (QD=1) and multi-queue (QD up to 1024)
• Random benchmarks: 4 KiB block reads/writes, single-queue and multi-queue (QD up to 1024)
• Flexible test parameters: configurable iteration count, test data (random/zero), measurement size (16 MiB–64 GiB), interval (0 s–10 min), and duration limit
• Dual units: view results in MB/s or IOPS; tooltips show both
• Copy-pasteable results: export measurements as formatted plain text

Example Output

Sequential Read 1MiB (QD=    8) :   832.04 MB/s [    793.5 IOPS]
Sequential Write 1MiB (QD=   8) :   773.81 MB/s [    738.0 IOPS]
    Sequential Read 1MiB (QD=1) :   667.96 MB/s [    637.0 IOPS]
   Sequential Write 1MiB (QD=1) :   576.30 MB/s [    549.6 IOPS]
     Random Read 4KiB (QD=  64) :   524.28 MB/s [ 127998.7 IOPS]
    Random Write 4KiB (QD=  64) :   192.25 MB/s [  46935.0 IOPS]
        Random Read 4KiB (QD=1) :    31.70 MB/s [   7738.3 IOPS]
       Random Write 4KiB (QD=1) :   200.17 MB/s [  48868.8 IOPS]

Requirements

• macOS 10.9.5 or later
• Xcode (to build from source)

Building

Open AmorphousDiskMark/AmorphousDiskMark.xcodeproj in Xcode and build the scheme. The app is sandboxed and requests user-selected file read/write access for target volume selection.

Architecture

The codebase is Objective-C, structured around a few key components:

File	Role
AppDelegate	Main UI controller — handles toolbar actions, volume selection, test orchestration
DiskMark	Core benchmark engine — manages threaded I/O with configurable block size, queue depth, and duration
DiskUtil	Volume enumeration via DiskArbitration framework, mount/unmount observation, filesystem metadata
DMTextView	Custom text view with logarithmic bar graph rendering (matching CrystalDiskMark’s visual style)
DMButton / DMButtonCell	Custom button with dark mode support
DMMediaIcon	Resolves storage device icons from IOKit kernel extension bundles
LinkTextField	Clickable URL text field

How benchmarking works

AmorphousDiskMark spawns threads to perform I/O against a temporary file on the target volume. The design mirrors CrystalDiskMark’s use of Microsoft’s diskspd parameters — block size, queue depth, thread count, duration, and warmup — adapted for macOS. Queue depth is implemented via concurrent threads (up to the macOS per-task limit of 2048) rather than POSIX AIO, which only supports 16 queues on macOS.

Usage

1. Select a target volume from the dropdown.
2. Click All (or an individual test button).
3. When finished, press ⌘S to save a screenshot, or copy the plain-text results.

Note: Avoid running write benchmarks more than necessary — repeated writes can reduce the lifespan of flash storage.

License

MIT License. See LICENSE for details.

UI design used with permission from the author of CrystalDiskMark.

Links

• Katsura Shareware
• CrystalDiskMark