linux 上的 msync 保证

Question

Is msync guaranteed to physically write dates into the hard-drive? Can I be 100% sure that if the OS crashes immediately after msync returns, that I won't lose data?

By 100% sure I mean that the data was physically written to the disk and not just hard drive buffer. Simply, I want to be sure that losing electricity won't result in loss of data.

Answer 1

It is still possible for data to be lost if the OS crashes after msync returns. Its because the data may still be stored in the file system cache and not yet written to the storage device. To guarantee that data is not lost in the event of an OS crash, you can use the fsync system call to synchronize the file system cache with the storage device. To be extra sure you should use a disk journaling filesystem like ext3, ext4, jfs, ntfs, reiserfs, xfs etc, that ensure that the filesystem remains consistent in case of a crash or power failure.