APFS file system bug causes a loss of data when writing to disk image
Backup software Carbon Copy Cloner developer Mike Bombich discovered a disk image bugs in the APFS file system of the macOS High Sierra system, which in some cases led to data loss. Mike Bombich explained to APFS data write problems he found while testing sparse disk images.
An ordinary disk image file (.dmg) is the same size as the actual disk it represents (though there is still space left unused), while a sparse image (sparse image) is only a fraction of the actual disk space used by the data. Sparse disk image file for the implementation of backup, disk cloning, and other operations, it is very flexible.
Bombich identified two issues. First, the free space on an APFS-format sparse disk image is not updated because it should be updated when there is less available space on the underlying physical host disk. The second problem is the lack of error reporting when a write request fails to dynamically grow a disk image, causing the data to be “written” empty. Bombic h traces both vulnerabilities back to the “diskimages-helper” application service on the macOS back end, and he has reported the issue to Apple. A sparse disk image is a disk image file that can be created by the disk utility under the macOS system.
When we upgraded our Mac to a High Sierra system, High Sierra automatically converted the disk to APFS. APFS is Apple’s new modern file system for SSDs that supports all modern Apple devices, from Apple Watch to iMac Pro. Common APFS partitions, such as SSD boot disks, do not have bugs, and the bugs found this time is usually found on disks that are connected to the network. Finally, Bombich said Carbon Copy Cloner will not support the APFS file system until Apple fixes the bug.
Source: MacRumors
