It's been over 24 hours now and there is no progress bar to know what is going on. Cancel is greyed out and I'm afraid that force quitting will damage the drive. Context: Plugged in an almost full 4 TB Seagate external drive to a Windows 7 PC to try and fix it after my Mojave Mac would either not mount it or fix it after it was incorrectly unplugged. The PC immediately suggested to run Scan and Repair saying the drive had errors. No unusual sounds, drive is flashing normally, doesn't seem to be hung or stuck, but >24 hours... Is that normal? What happens if I force quit? Will my Mac now read it? Will it need to be repaired again? With what app and how long will it take? The drive is 4 months old and has always been treated with care.
13 Answers
I think this is one of those instances where your patience has to be directly proportional to the time since your last backup.
Whether the repair has failed or is just running extremely slowly, suddenly terminating it mid-process is never going to improve matters.
You can be pretty certain that unless or until it tells you it's finished… it hasn't.
If your backup is up to date, just pull the plug then see if it will format.
3Is that normal?
How long? Hard to say. In 1998, such a task might take nearly an hour, perhaps even a few. Around 2008, a standard desktop drive took around 7-11 hours to do a full, non-quick format. Since then technology has become faster, but drive size has also increased. USB is most often not the fastest available connection method.
What happens if I force quit?
If you quit early, you may have an incomplete repair. This can be bad, because the data is likely stored using some tables/charts, and so if a repair isn't complete then some of the pointers may be inconsistent with where data is, which may result in a loss.
However, an even worse scenario is if the repair tool fails. If invalid data is found and not corrected, it might be used. Then, the repair tool might misinterpret that data and use it incorrectly. By pointing to the wrong data, it might find something else that doesn't make sense, and try to repair that too, making more adjustments based on errorneous/nonsense data. You can make the data on a drive hideously infeasible to recover. (Not necessarily impossible, technically, but 4 Terabytes is around 4 trillion bytes... that would be quite a lot to need to investigate manually.)
The good news is that this is unlikely to cause any hardware errors. The threats described above are why the ideally-recommended approach is for a bit-for-bit (sometimes called "forensic") backup copy should be made before any such repair. Not doing that can risk longer recovery. (In really unfortunate cases of insufficient backup, data recovery might not be reasonably easy at all.)
A "force quit" may reduce the chances of the drive ending in a consistent state. On the other hand, if the repair tool did get confused and is going around in circles, damaging data structures, then stopping it might cause some data to be preserved and more easily recovered than letting it keep going.
Of course, if the software is not making any further progress, which is especially likely if hardware froze up, then you might have no other options except to "force quit" some hour/someday.
Will my Mac now read it?
Depends on the state of the data structures on the disk. There is no universal answer for that.
Will it need to be repaired again?
If the hardware is good, then the worst-case scenario is that the drive could have its partitions reformatted (or, slightly worse, needing to re-partition), and then the drive may work fine. Of course, that may result in significant data loss.
With what app and how long will it take?
To recover data:
TestDisk can be useful. (Despite its name, it is more about data recovery than testing.) It is not necessarily the easiest software on the planet, but then again, many of these recovery tools aren't.
Other "forensic" software exists that may be helpful.
To repair a drive: there are various repair software out there. But in general, most of them work reasonably well, failing only for good causes like existing data structures already being problematic. In that case, trying other repair tools will probably just result in similar problems, so the best bet is to just make sure you have data backed up, and then re-format the drive (re-partition if needed) and then recover from backup.
I realize that some of the advice given in this answer may become less feasible after some actions are taken. There is no sensibly easy way to recover from certain scenarios. That is why well-funded people/organizations typically just avoid such scenarios, by having good backups (especially before certain actions get taken, like intentionally/manually initiating some "repair" software).
Thank you. I weighed the pros and the cons and did an "end task" at 28 hours. Fortunately, the PC reads it , the files seem to be there. I think the next step is to recover the most important files, which are from mac apps. I read somewhere that the reason why it wouldn't mount on my mac is because it is unmounting it and scanning it in the background after it was incorrectly unplugged. I think it would be convenient to keep it from automatically scanning in the bg on my mac... the idea would be to copy all the files to a safe location from the PC, then plug it onto my mac with auto-scanning off and trying to recover the most important files (a video I was supposed to hand in yesterday morning). The reformat the whole thing.Anyway, I'm writing this in case it helps anyone else.
