Hello all, I implemented a write workload by sequentially appending to the file end using libaio aio_write in O_DIRECT mode (with proper offset and buffer address alignment). When I reach a 1MB boundary I call fallocate() to extend the file. I need to protect the write from various failures such as disk unplug / power failure. The bottom line is, once I ack a write-complete, the user must be able to read it back later after a disk/power failure and recovery. In my understanding, fallocate() will preallocate disk space for the file, and I can call fsync to make sure the file metadata about this new space is persisted when fallocate returns. Once aio_write returns the data is in the disk. So it seems I don't need fsync after aio-write completion, because (1) the data is in disk, and (2) the file metadata to address the disk blocks is in disk. On the other hand, it seems XFS always does a delayed allocation which might break my assumption that file=>disk space mapping is persisted by fallocate. I can improve the data-in-disk format to carry proper header/footer to detect a broken write when scanning the file after a disk/power failure. Given all those above, do I still need a fsync() after aio_write completion in XFS to protect data persistence? Thanks all for your input! regards, Shawn
