Is NTFS fail-safe in case of a power outage?

Theory aside, there are so many problems to be found on this site, caused on NTFS by power outage, that the answer has to be : NO.

I have personally handled on this site problems that went from suddenly appearing bad sectors and up to Windows installation completely hosed.

A computer is an extremely complex hardware, and modern hard disks have also become small computers of their own. Each has its own processor and memory, so each is vulnerable to power glitches happening at the wrong moment.

Even if NTFS is fail-safe (which I don't really believe), the components that handle changes to the hard disk are certainly not fail-safe. So the whole question is quite academical and doesn't relate to the real world.

The answer then has to be that NTFS is safer, but not fail-safe.

NTFS only journals metadata, which prevents corruption of the file system, but God help you with the data, which is not journaled. If a power outage occurs during write, data is lost.

After writing code that reads and write NTFS, I came to the conclusion that the NTFS recovery feature is designed / implemented in a flawed manner.

The NTFS journal contains a log entry for the operation that caused the write, it usually contains just enough information to undo / redo that operation, however, if the sector is corrupted during the write (due to power failure), the log entry is not necessarily enough to recover all the metadata in that sector.

The Windows NTFS driver implementers assume that any write operation will either completely succeed or not happen at all (this is only true in some enterprise environments).