On 28/02/19 09:41, Ingo Franzki wrote:
Well, there are the following 2 commands:
Get physical block size:
blockdev --getpbsz <device>
Get logical block size:
blockdev --getbsz <device>
I didn't know the blockdev command and, to recap, we have:
--getpbsz: physical sector size
--getss: logical sector size
--getbsz: blocksize used internally by the kernel
getpbsz/getss correspond to physical/logical sector size reported by
fdisk, smartctl, etc.
Filesystems seem to care about the physical block size only, not the logical
block size.
So as soon as you have PVs with different physical block sizes (as reported by
blockdev --getpbsz) I would be very careful...
I've done the test suggested by Stuart and it seems to contradict this.
I have pvmoved data from a 512/512 (logical/physical) disk to a newly
added 512/4096 disk but I had no data corruption. Unfortunately I
haven't any native 4k disk to repeat the same test.
Here is what I've done.
/dev/sdb: SSD with 512/512 sector size
/dev/sdc: mechanical disk with 512/4096 sector size
# blockdev -v --getss --getpbsz --getbsz /dev/sdb
get logical block (sector) size: 512
get physical block (sector) size: 512
get blocksize: 4096
# blockdev -v --getss --getpbsz --getbsz /dev/sdc
get logical block (sector) size: 512
get physical block (sector) size: 4096
get blocksize: 4096
# pvcreate /dev/sdb4
# vgcreate vgtest /dev/sdb4
# lvcreate -L 1G vgtest /dev/sdb4
# mkfs.ext4 /dev/mapper/vgtest-lvol0
# mkdir /media/test
# mount /dev/mapper/vgtest-lvol0 /media/test
# cp -a SOMEDATA /media/test/
# umount /media/test
# fsck.ext4 -f /dev/mapper/vgtest-lvol0
Filesystem created and no error on it. Now the disk with different
physical size:
# pvcreate /dev/sdc1
# vgextend vgtest /dev/sdc1
# pvmove /dev/sdb4 /dev/sdc1
# fsck.ext4 -f /dev/mapper/vgtest-lvol0
# mount /dev/mapper/vgtest-lvol0 /media/test
# ls /media/test/
The fsck command reports no errors, the filesystem is mountable and the
data is there.
Looks like physical sector size didn't matter here. Or I'm missing
something?
Cesare.
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