--mixed seems to prevent selection of alternative leaf/node/sector sizes: $ sudo mkfs.btrfs --mixed -n 16384 -s 16384 -d single -m single /dev/mapper/ca-store Created a data/metadata chunk of size 8388608 fs created label (null) on /dev/mapper/ca-store nodesize 16384 leafsize 16384 sectorsize 16384 size 98.00MB $ sudo mount /dev/mapper/ca-store /mnt mount: /dev/mapper/ca-store already mounted or /mnt busy Apr 6 17:59:36 s_all@ruthven kernel: [1842232.007361] device fsid 8ca4524f-4cd4-45a6-855b-dc14b56652e3 devid 1 transid 4 /dev/mapper/ca-store Apr 6 17:59:36 s_all@ruthven kernel: [1842232.117266] btrfs: disk space caching is enabled Apr 6 17:59:36 s_all@ruthven kernel: [1842232.117271] btrfs flagging fs with big metadata feature Apr 6 17:59:36 s_all@ruthven kernel: [1842232.117657] btrfs: Incompatible sector size(16384) found on dm-10 Apr 6 17:59:36 s_all@ruthven kernel: [1842232.118023] btrfs: open_ctree failed $ sudo mkfs.btrfs --mixed -n 16384 -l 16384 -d single -m single /dev/mapper/ca-store Created a data/metadata chunk of size 8388608 fs created label (null) on /dev/mapper/ca-store nodesize 16384 leafsize 16384 sectorsize 4096 size 98.00MB $ sudo mount /dev/mapper/ca-store /mnt mount: /dev/mapper/ca-store already mounted or /mnt busy Apr 6 18:06:37 s_all@ruthven kernel: [1842652.655610] device fsid 70c12f3f-39af-41e2-afa5-8b807ae2e410 devid 1 transid 4 /dev/mapper/ca-store Apr 6 18:06:37 s_all@ruthven kernel: [1842652.777797] btrfs: disk space caching is enabled Apr 6 18:06:37 s_all@ruthven kernel: [1842652.777806] btrfs flagging fs with big metadata feature Apr 6 18:06:37 s_all@ruthven kernel: [1842652.777812] btrfs: unequal leaf/node/sector sizes are not allowed for mixed block groups on dm-10 (It''s not particularly important to me in this configuration -- I can just use 4096, but I thought it should be published). Hugo. -- === Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk == PGP key: 65E74AC0 from wwwkeys.eu.pgp.net or http://www.carfax.org.uk --- Computer Science is not about computers, any more than --- astronomy is about telescopes.