要求linux 内核3.8以上
在线改变已经挂载的ceph 块设备容量：
# rbd create --size 10000 test
# rbd map test
# mkfs.ext4 -q /dev/rbd1
# mount /dev/rbd1 /mnt
# df -h /mnt
Filesystem Size Used Avail Use% Mounted on
/dev/rbd1 9.5G 22M 9.0G 1% /mnt
# blockdev --getsize64 /dev/rbd1
10485760000
# rbd resize --size 20000 test
Resizing image: 100% complete...done.
# blockdev --getsize64 /dev/rbd1
20971520000
# resize2fs /dev/rbd1
resize2fs 1.42 (29-Nov-2011)
Filesystem at /dev/rbd1 is mounted on /mnt; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 2
The filesystem on /dev/rbd1 is now 5120000 blocks long.
# df -h /mnt
Filesystem Size Used Avail Use% Mounted on
/dev/rbd1 20G 27M 19G 1% /mnt
此方法只对格式化未EXT4文件系统的块设备有效。对于XFS，要再 resize之后执行
# xfs_growfs /mnt
文章翻译自：http://dachary.org/?p=2179&utm_source=tuicool
