Using _ftruncate_ or FALLOC_FL_ZERO_RANGE is a bad idea for a database. The problem is that you may get an out of disk space error mid operation. If you are us

Using _ftruncate_ or FALLOC_FL_ZERO_RANGE is a bad idea for a database. The problem is that you may get an out of disk space error mid operation. If you are using mmap, that will express itself as a segmentation fault, which you really don't want. You _need_ to allocate the file ahead of time, so you can properly behave there.