It checksums metadata [1]: http://dtrace.org/blogs/ahl/2016/06/19/apfs-part5/ http://dtrace.org/blogs/ahl/2016/06/19/apfs-part5/ From the same article: the eng

It checksums metadata [1]: http://dtrace.org/blogs/ahl/2016/06/19/apfs-part5/ http://dtrace.org/blogs/ahl/2016/06/19/apfs-part5/ From the same article: the engineers contend that Apple devices basically don’t return bogus data. NAND uses extra data, e.g. 128 bytes per 4KB page, so that errors can be corrected and detected. (For reference, ZFS uses a fixed size 32 byte checksum for blocks ranging from 512 bytes to megabytes. That’s small by comparison, but bear in mind that the SSD’s ECC is required for the expected analog variances within the media.)