On Sun, Jan 4, 2015 at 8:18 AM, Marc MERLIN <marc@xxxxxxxxxxx> wrote: > badblocks are a thing of the past, as you hinted drives automatically > remap badblocks so that the filesystem doesn't have to deal with them. > > If you have a questionable drive, you can indeed simply dd 0's over it > before you use it with btrfs. I suggest badblocks because the default works on both 512 or 4096 byte physical sector drives. On AF 512e drives, dd default block size of 512 bytes will fail if a bad sector is encountered. What happens (to at least one model of drive since I've had this happen to me) is the 512 byte write to a bad 4096 byte sector gets interpreted by the drive as a Read Write Modify. So do use dd you need to also use bs= setting it to a multiple of 4096. Of course most people using dd for zeroing set bs= to a decently high value because it makes the process go much faster than the default block size of 512 bytes. I just used strace on badblocks and by default issues 64KiB writes (the block size is 1024 bytes with a count of 64, which looks like it gets aggregated). -- Chris Murphy -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
