Of course fsync() sends a flush to the disk (unless you use non-standard mount options or "eatmydata"). They may not honor the FUA bit, though, but hopefully no

Of course fsync() sends a flush to the disk (unless you use non-standard mount options or "eatmydata"). They may not honor the FUA bit, though, but hopefully nobody relies on this if they expect it to work with consumer disks (See e.g. here https://devblogs.microsoft.com/oldnewthing/20170510-00/?p=95505 https://devblogs.microsoft.com/oldnewthing/20170510-00/?p=95... ). What I have heard is that some disks have problems if they are on a error recovery path. E.g. they have a corrupt sector or a sector that needs reallocation (pending sector), and then they have a power failure while the sector is reallocated.