fallocate doesn't do any IO; it's much faster. From the fallocate man page: > For filesystems which support the fallocate system call, preallocation is done q

fallocate doesn't do any IO; it's much faster. From the fallocate man page: > For filesystems which support the fallocate system call, preallocation is done quickly by allocating blocks and marking them as uninitialized, requiring no IO to the data blocks. This is much faster than creating a file by filling it with zeros.