3 ms·
Without the direct flag dd is pretty pointless. However, with the direct flag, you do un-bufferred I/O with precisely controlled block size. It the fastest way
by derekzhouzhen 4y ago
Without the direct flag dd is pretty pointless. However, with the direct flag, you do un-bufferred I/O with precisely controlled block size. It the fastest way to ensure the data really go where you want it to go, in the fashion you like it to be, right at the moment.
- thanatos519 4y agoRight! Apparently Linux has a facility for 'optimal IO size' of block devices (see 'lsblk -o NAME,OPT-IO') but on my system I only have a value for Linux md RAID devices (which happen to be RAID0, and the OPT-IO value is the stride). All of the other devices have OPT-IO 0. Perhaps more work needs to be done to bubble some value up from the hardware.