iOS resurrected photo bug fixed with iOS 17.5.1 detailed by Apple

In other words, when a photo is deleted in the library, it is truly deleted in the OS. However, because of how NAND storage works, the memory used to store the photo is marked as available rather than immediately deleted.

That has nothing to do with NAND - that's just how filesystems work.  But what *is* because of how NAND works, that space marked as unused should have been TRIMmed for performance and wear-leveling purposes.  I've never heard of an OS that doesn't do that - it's shocking to learn iOS apparently doesn't.

maltz said:

In other words, when a photo is deleted in the library, it is truly deleted in the OS. However, because of how NAND storage works, the memory used to store the photo is marked as available rather than immediately deleted.

That has nothing to do with NAND - that's just how filesystems work.  But what *is* because of how NAND works, that space marked as unused should have been TRIMmed for performance and wear-leveling purposes.  I've never heard of an OS that doesn't do that - it's shocking to learn iOS apparently doesn't.

Correct about NAND and filesystems. But there's still a giant steaming pile of bullsh!t here, and it has nothing to do with whether or not TRIM is implemented. (And BTW it would be a mistake to infer from this nonsense that TRIM isn't implemented.)

Filesystems are a series of blocks. When blocks are released back to the filesystem, they no longer have any connection to each other. There is no realistic mechanism by which free filesystem space could magically reappear as the file it once was. You'd need purpose-built software to try to reconstruct a deleted file, and it may actually be impossible on a filesystem like APFS. (It was not on HFS; several companies sold such software.) And even if somehow that file got reconstituted, there's no mechanism by which it could suddenly reappear in the Photos app.

What Apple probably said, which got mangled by the reporter, is:

- the photo was marked for deletion in Photos. This does nothing to the file itself, it's just marked as due to be deleted in the Photos database.

- due to some corruption in the Photos database, the file wasn't deleted upon expiry, and some vestige of its metadata was left in the database.

- in 17.5, some new error detection and correction code was added to Photos. It detected those vestiges and fixed the database, returning the photo to its album.

In all this, nothing happened to the file itself.

Assuming Apple isn't lying about it all being on-device, this is probably the only possible scenario.

A few of us suggested it was likely a local device glitch when this broke, but certain folk pointed fingers at Apple's iCloud security.  Hopefully they will fall on their knees and apologise ;)

maltz said:

That has nothing to do with NAND - that's just how filesystems work.  But what *is* because of how NAND works, that space marked as unused should have been TRIMmed for performance and wear-leveling purposes.  I've never heard of an OS that doesn't do that - it's shocking to learn iOS apparently doesn't.

I've never heard of a filesystem on any OS that invokes TRIM on every file delete — that would be wildly inefficient. TRIM was designed for regular, custodial duties, run daily or hourly, wasn't it? A lot can happen to a file system in that kind of time.

I think it was important that Apple explained why this happened to certain users. I know people will blow this off as a PR stunt and think it's just Apple covering its ass but to me it's a very logical explanation that most users won't comprehend because they're most likely not tech savvy. They just see news headlines and run with it not knowing or understanding why something like this actually happened. But it's great for the Apple haters out there who will just stupidly take these headlines and run with them thinking they're cool and funny.