The TL DR is that writing to macOS Disk Images – whether plain. This article presents a lot more data, which both clarify and confound. There’s a new twist: results differ when the image is still mounted after creation, and after unmount-remount.Įnc UDRW is 55 MB/s first time, 900 remounted Įnc UDSB is 360 first, 4.3 GB/s remounted

unencrypted disk images used as Block Device storage in virtualisation.both encrypted and unencrypted sparse bundles used for shared Time Machine backup storage.encrypted disk images used as a substitute for the absence of folder encryption in APFS.However, that has now changed, with write performance becoming important to the user in: This difference may reflect Apple’s historical usage of disk images, which have been most commonly used for reading rather than writing. Given the high write performance of the SSDs used, this can only indicate that macOS is intentionally throttling threads responsible for performing writes to the encrypted disk image, and to unencrypted disk images too. The sparse bundle was least impaired, with a write speed just under half that of the SSD, but all three disk images wrote at less than 20% of SSD speed, with the encrypted disk image the worst of all, at less than 1%. While reading from each of the Disk Images was almost as fast as from the SSD, write speeds were severely reduced.

Mac disk image