Last Week on My Mac: Should we be worried about data integrity?

All forms of data storage are subject to failure. Whether they’re clay tablets in an ancient civilisation, books in a library, or bits encoded in electronic media, sooner or later they’ll become corrupted or lost altogether. The only uncertainties are when, and what measures we need to take to postpone that event. In this context, how should we monitor the integrity of data stored in and for our Macs? Is APFS as a file system sufficient, or do we need something more?

This takes us back to a time when some inside Apple were keen to adopt the youthful ZFS. Despite enthusiasm and initial ports of the file system, the decision was made to develop Apple’s own proprietary file system APFS instead, and ever since those who have come to love ZFS have drawn attention to what they see as shortcomings, most notably in the lack of support for file data integrity checks in APFS.

APFS does have integrity checks built into the file system itself, in the form of Fletcher 64 checksums in the header of each file system object, but none that apply to file data, in the way that ZFS does, and checks those during data scrubbing. Doesn’t this make APFS prone to events such as bit rot?

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