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My computer was rendering and doing batch file operations on the local hard drive but the battery on it reached the threshold of charge where Windows would go into hibernate mode while processing.

I'm curious if, say a program was in the middle of modifying a file and the battery reached the critical level, would Windows just take a snapshot of the current state? Or would it just tell all programs to finish the last I/O operation and then suspend? Would there be any chance of corruption?

Any input would be appreciated. At the moment, I fear for my file's integrity.

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4 Answers

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Keep in mind that I/O operations on NTFS filesystems are atomic, as with other journaling file systems--if an I/O operation is not complete and must be interrupted, the system will roll back the I/O operation. The application probably is writing in chunks and your file may not be complete, but it should be able to resume properly once you turn your computer back on.

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If the system rolls back the I/O operation, does the system attempt to start again at the previous rolled back I/O operation or does it skip it? – Kevin Hua Jul 11 '12 at 22:36
The application may not see this and the I/O operation may end up getting skipped. You just have to hope that the last I/O operation was completed. On hibernation, the I/O operation in progress should be completed, but it is possible that the operation does not finish, resulting in data loss. From my experience, this scenario doesn't appear to be likely to happen, as individual I/O operations tend to be small. – DragonLord Jul 11 '12 at 22:39
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Unless you've made custom changes to your battery settings, at critical level, you will almost always have a bit more % of battery power left, even if the system hibernates. The answer is it depends on the task you were doing when system went into hibernation and how the application takes priority over the system. If you could post exactly what you were doing (application, file type, etc) I think you would get a better response from the community here. If you'd like to elaborate on some specifics, I might be able to help you.

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When I resumed the computer, the files seemed okay and battery was at 5%. I have no idea how to verify the hashes to see if it would've made a difference. I was using a fairly unknown/uncommon program, rt-booster, which essentially mounts a Windows Imaging Format file, and removes/modifies the mounted files in a sequential order depending on the options the user chooses. After the modification is done, rt-booster unmounts the WIM and commits it to the hard drive. – Kevin Hua Jul 11 '12 at 22:27
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I believe that the way that hibernation works is that it freezes everything that is going on at the moment (all operations are discrete, so there is a stopping point) and then writes whatever is in RAM to the hard drive.

On restore, it just reverses this process.

The times when corruption could occur or programs could crash is if they are dependent on time (or a small number of other things, but those are far less common). If something expects that a task has been done the previous minute, and it looks back and sees what was written 2 hours ago, that could cause a problem (depending on the program). Another common type of problem is if your machine was using the network, that will shut down while the computer is in hibernation, as will all other peripherals.

If you machine has already gone into hibernation, there is nothing you can do to fix it. You just have to make sure that hibernation does not take place to begin with.

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There's always a chance of corruption with hibernation.

The hardware configuration can change completely while the computer hibernates. The location where it was writing the file might not even exist anymore.

Maybe because it was a location on the network or a USB key. Maybe the local harddrive was locked with BitLocker and your TPM breaks...

The only thing that can be truthfully said is: "It usually works".

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