Disk Image Performance With macOS 26.3.1
This table summarises read and write performance of the most popular types of disk image prior to macOS Tahoe, and demonstrates how sparse bundles have consistently performed best and most consistently, and sparse images (now dropped from Disk Utility’s options) fare worst, particularly when encrypted.
Although most of the test results in macOS 26.3.1 are very similar to those from 26.0, performance when using 256-bit AES encryption has fallen for all three disk image types, and most significantly in write performance for RAW and ASIF images, which have reduced from 4.3 to 1.58 GB/s (RAW) and from 3.9 to 1.72 GB/s (ASIF). The magnitude of those reductions is sufficient to have obvious impact on their use. Compared to native write performance using FileVault of 7.66 GB/s, those two types of disk image are pedestrian in the extreme, turning that blisteringly fast SSD into the equivalent of 20 Gbps over USB 3.2 Gen 2×2.
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When their folder-based structure is acceptable, UDSB sparse images remain the disk image type of choice, for their consistent high performance even when encrypted.
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As [ASIF] sparseness isn’t dependent on APFS trimming habits, they are now an alternative that can be used on network storage and NAS. However, those able to use sparse bundles should continue to do so, particularly if using encryption.
Previously:
- macOS 26.3.1
- DropDMG 3.7
- ASIF Disk Images in macOS Tahoe
- How Disk Images and VMs Are More Efficient
- Disk Images in Sequoia
