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MacOS may lose data on APFS-formatted disk images

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Re: MacOS may lose data on APFS-formatted disk images

#151
post #13

High Sierra seems like a real gem.

I postponed upgrading because of reported issues with the original Magic Trackpad, and it looks like a dodged a real bullet right there.

Every few months, just as soon as I start thinking maybe I should give in to Apple’s incessant nagging and dark-pattern prompts to upgrade, stuff like this comes up.

I think I’ll just wait for the new release, or for a time when I’m ready to wipe any machine I want to upgrade.

Re: MacOS may lose data on APFS-formatted disk images

#153
post #72
post #64

Earlier quoted context omitted.

No, APFS must be usable on USB drives and so on. That would be a fatal design flaw.

From http://dtrace.org/blogs/ahl/2016/06/19/apfs-part5/ : "Explicitly not checksumming user data is a little more interesting. 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. NAND uses extra data, e.g. 128 bytes pe…

ZFS is the only widely deployed file system to do data checksumming by default though. You can’t blame APFS for not doing it when no other file system does it either.

Re: MacOS may lose data on APFS-formatted disk images

#154
post #131

Earlier quoted context omitted.

I “lost” a lot of space due to time machine local backups. It was frustrating to research and I thought there was something seriously wrong with my computer. Try deleting the local backups and see if you get some space back

I had to make room on my MBP SSD to install windows through bootcamp and bashed my head against a wall on the same issue. It took me half an hour to find the reason why so much of my hard drive wasn't available despite me having deleted almost all third party apps and personal data on my macOS partition. Time Machine does 'local backups' and there is NOWHERE in the user interface that fully explains the space they oc…

Yes it’s a really poor design decision. They could have at least added “local time machine backups” color to Disk Utility, or added a way to turn them off.

Agreed re: snappiness of other OS. Ubuntu flies on my 2013 MBP.

Re: MacOS may lose data on APFS-formatted disk images

#155

Can you even test a filesystem properly internally? Seems to me we're all involved in a massive public beta.

Externally "testing" a filesystem isn't exactly easy either. If an error occurs, there's not gonna be an exception thrown that you can send off to telemetry.

If you're lucky, your customer notices that files are missing, understands that it has to be a bug in the operating system and maybe even has a rough idea what they were doing that caused the bug to occur, then calls up support and your first-level support is competent enough to direct the problem to the filesystem people and then it's still going to require a lot of luck for that department to reproduce the problem and to actually find out what in the code is causing it.

Re: MacOS may lose data on APFS-formatted disk images

#156

Earlier quoted context omitted.

Anecdata != filesystem issue. If you have more information about the problem you encountered and how it implicates/interacts with APFS, please do link to it. Otherwise, bug reports via circumstantial evidence are, while not inherently false, certainly suspect.

You asked for an example, and you got it.

You're confusing your posters. freehunter asked for an example. zbentley complained that it was anecdata/specious.

Re: MacOS may lose data on APFS-formatted disk images

#157
post #86

Earlier quoted context omitted.

How do you know that? Filesystem corruption is frequently silent, and every-time it happens customers don't get on the phone and send the disks to apple so that they can root cause the problem. Its quite possible this bug has happened an untold number of times before it happened to someone who went through the effort to reproduce and isolate it.

We know that because it was deployed to almost a billion devices without a problem. If there was a problem that affected even a fraction of a percent of people, it would have been all over the news given how many devices that is. Edit: Thanks for the downvotes. If you disagree, please tell me why. Apple's deployment of APFS to iPhones was so flawless, most people probably still don't even know they did it.

The downvotes will be because you're adding nothing to the conversation. You're just repeating your grandparent post's point.

Re: MacOS may lose data on APFS-formatted disk images

#158
post #72
post #64

Earlier quoted context omitted.

No, APFS must be usable on USB drives and so on. That would be a fatal design flaw.

From http://dtrace.org/blogs/ahl/2016/06/19/apfs-part5/ : "Explicitly not checksumming user data is a little more interesting. 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. NAND uses extra data, e.g. 128 bytes pe…

But if they're so confident in the disk, then why do they checksum the metadata? They should either trust the disk and have no checksums or not trust the disk and checksum everything.

There are plenty of other reasons not to checksum user data, as it's a choice many have made, but that they trust the disk is an invalid argument.

Re: MacOS may lose data on APFS-formatted disk images

#159

Earlier quoted context omitted.

Rene Ritchie is very biased. He has to be as his livelihood depends on Apple. I take his words with many grains of salt. The only reason he's quoting Sinofsky is because it gives him a way of excusing Apple's software stumbles of late.

Rene Ritchie is very biased. He has to be as his livelihood depends on Apple. No, he quoted Sinofsky because he’s one of the few people in the world who understands what it’s like trying to operate at this scale, since he was at Microsoft during it’s heyday. Corner cases that affect only .01 percent of the installed bases aren’t a big deal when you’re operating at a few million; it’s entirely different when it’s more…

The software issues haven't been corner cases lately. iOS 11 is just... bad software. High sierra has had some rather embarrassing issues too and, I'll say again, they aren't corner cases.

Re: MacOS may lose data on APFS-formatted disk images

#160

Earlier quoted context omitted.

Wait, why would the 50 GB need to be transferred fully every time if it was a fixed size image?

The very first backup of a fixed size image will be the full size of the image, e.g. 50 GB, no matter which backup software you use. Even if inside the image no files exist. The very first backup of a sparse bundle disk image will be ~100 MB (the initial size of that image). On repeated backups, some backup softwares operate on file level and upload the whole file if it changed. So if you have a fixed size 50 GB imag…

Sure, but any halfway competent backup program would split it into chunks before deduplication anyway, rendering the exercise pointless.
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