During runtime my program creates and writes two large binary files simutaneously to the disk. File A is about 240GB, file B is about 480GB. The two files are maintained by two ofstream objects, and the write opertations are performed with the member funcion write in a loop.
Now the problem is: The write file operation fails everytime the whole write file procedure reaches 63~64%. The first time it failed on file A, and the second time it failed on file B.
During the program runs these days, the power supply of my building happens to be under upgrade. By a strange coincidence, every time the program failed, the electrician happened to be cutting and resuming the power supply of the central air-conditioner and some offices. Therefore, I really wonder whether the write file failures were caused by unstable power supply.
I’m sure that the failure is not caused by file size limit, because I’ve tried to write a single 700GB file using the same method without any problem.
Is there any way to find out the detailed reason? I feel that the flags (badbit, eofbit and failbit) of ofstream don’t provide too much information. Now I’m trying to use errno and strerror to get the detailed error message. However, I see that a possible value of errno is EIO, which measn “I/O error”, which again provides no useful information.
Is there anyone who encountered this situation before?
By the way, the program runs without error when the sizes of file A and file B are small.
PS: This time the program fails at 55%, and the errno value is EINVAL: Invalid argument. Very strange.
Confirmed, the cause is indeed a bug of NTFS: A heavily fragmented file in an NTFS volume may not grow beyond a certain size. This means that CreateFile and WriteFile cannot fundamentally solve the problem, either.