关于redhat做软raid0出错的问题！

gui555

做过raid过程如下：
两个虚拟硬盘sda,sdb，sda2是/分区，里面已经有系统，用了54%,sdb1是/date分区，跟sda2差不多大，略大一点。
1，先用fdisk指定了fd
2,编辑/etc/raidtab
raiddev /dev/md0
raid-level 0
nr-raid-disks 2
nr-spare-disks 0
persistent-superblock 1
chunk-size 4

device /dev/sda2
raid-disk 0
device /dev/sdb1
raid-disk 1
3,mkraid /dev/md0 命令后出错，显示
analyzing super-block
disk 0: /dev/sda2, 3831502kB, raid superblock at 3831424kB
/dev/sda2 is mounted
mkraid: aborted.
(In addition to the above messages, see the syslog and /proc/mdstat as well
for potential clues.)

哪里错了？