On Wed, 16 Jul 2025 15:30:20 +0100 Filipe Maia <filipe.c.maia@xxxxxxxxx> wrote: > Hi, > > When a 4Kn disk is added to an mdadm array with sector size 512, its > sector size changes to 4096 to accommodate the new disk. > > Here's an example: > > ``` > truncate -s 1G /tmp/loop512a > truncate -s 1G /tmp/loop512b > truncate -s 1G /tmp/loop512c > truncate -s 1G /tmp/loop4Ka > losetup --sector-size 512 --direct-io=on /dev/loop0 /tmp/loop512a > losetup --sector-size 512 --direct-io=on /dev/loop1 /tmp/loop512b > losetup --sector-size 512 --direct-io=on /dev/loop2 /tmp/loop512c > losetup --sector-size 4096 --direct-io=on /dev/loop3 /tmp/loop4Ka > mdadm --create /dev/md2 --level=5 --raid-devices=3 /dev/loop[0-2] > # blockdev returns 512 > blockdev --getss /dev/md2 > mdadm /dev/md2 -a /dev/loop3 > mdadm /dev/md2 -f /dev/loop2 > # blockdev still returns 512 > blockdev --getss /dev/md2 > mdadm -S /dev/md2 > mdadm -A /dev/md2 /dev/loop0 /dev/loop1 /dev/loop3 > # blockdev now returns 4096 > blockdev --getss /dev/md2 > ``` > > This breaks filesystems like XFS, with new mounts failing with: > `mount: /mnt: mount(2) system call failed: Function not implemented.` If you dd the XFS image from an old 512b disk onto a newly bought large 4K-sector HDD, would it also stop mounting on the new disk in the same way? Perhaps something to be improved on the XFS side? -- With respect, Roman
