[favorited]

> data integrity checksums

I believe it has checksums on its own metadata, but no checksums on actual user data. So you won't lose a whole folder or volume due to bitrot, but it doesn't provide protection against a flipped bit in one of your photos.

[frankjr]

I wonder why they don't do checksums on data. Too complex? Is bitrot not a common problem on modern SSDs? It's also not clear what should a user do after they've received a notification that a scrub found a mismatch. It's not like you can replace the soldered on SSD... It would be still great for external ones though.

[arp242]

They claimed it's not needed because Apple hardware is very good; from [1]:

"The APFS engineers I talked to cited strong ECC protection within Apple storage devices. Both flash SSDs and magnetic media HDDs use redundant data to detect and correct errors. The engineers contend that Apple devices basically don’t return bogus data."

Note this continues for a bit and criticises that position. Also see the HN discussion at the time: https://news.ycombinator.com/item?id=11934457

I don't think it's a good decision either; obviously you can run systems without checksums (we've been doing so for decades) but "netter safe than sorry" seems to be the smart thing. It's pretty cheap to checksum data, which is why all the next-gen filesystems (ZFS, btrfs, bcachefs) do so.

[1]: https://ahl.dtrace.org/2016/06/19/apfs-part1/

[frankjr]

Yeah it's strange and quite disappointing. Even if Apple devices never returned bogus data (doubtful), there's a whole industry of external disks, largely fuelled by Apple's ridiculous SSD prices, that you're putting APFS on and which are often of dubious quality. Then again, the interview is now 8 years old and they must have been working on something since.