No filesystem, regardless of what kind of journaling is used, can guarantee anything else except that after a power failure you will get the same filesystem as it was a few minutes before the power failure.
If there was anything written to the HDD/SSD during those minutes, it would be lost.
For better guarantees than this you need special hardware, e.g. SSDs with big capacitors that can maintain the local power supply for a fraction of a second, during which the SSD controller can flush to non-volatile storage all buffered data.
If there was anything written to the HDD/SSD during those minutes, it would be lost.
For better guarantees than this you need special hardware, e.g. SSDs with big capacitors that can maintain the local power supply for a fraction of a second, during which the SSD controller can flush to non-volatile storage all buffered data.