fdisk /dev/mapper/mpath50
....
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
WARNING: Re-reading the partition table failed with error 22: Invalid argument.
The kernel still uses the old table.
The new table will be used at the next reboot.
解决办法：
Run "kpartx -a" after FDISK is completed to add all partition mappings on the
newly-created multipath device
[root@www mapper]# ls -l mpath50*
brw-rw---- 1 root disk 253, 8 Jan 31 10:59 mpath50
[root@www mapper]#
[root@www mapper]# kpartx -a /dev/mapper/mpath50
[root@www mapper]# ls -l mpath50*
brw-rw---- 1 root disk 253, 8 Jan 31 10:59 mpath50
brw-rw---- 1 root disk 253, 25 Jan 31 11:01 mpath50p1