原本系统是centos 6.5 使用两颗750G硬盘作Raid 1，
最近因为资料增多，将硬盘依序换成两颗2T的，磁区重切资料也重建起来了，
但是可使用总空间依然是只有750G，不知道该怎么作才能将
md2的 sda3 sdb3原本总空间从720G增加至1940G呢? 谢谢各位
以下是目前2颗2T硬盘的相关资料‧
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/md2 715654448 158977492 520317084 24% /
tmpfs 1985868 80 1985788 1% /dev/shm
/dev/md1 1015640 86412 876804 9% /boot
md1 : active raid1 sda2[2] sdb2[3]
1048512 blocks super 1.0 [2/2] [UU]
bitmap: 0/1 pages [0KB], 65536KB chunk
md0 : active raid1 sdb1[3] sda1[2]
4192192 blocks super 1.1 [2/2] [UU]
md2 : active raid1 sdb3[3] sda3[2]
727197504 blocks super 1.1 [2/2] [UU]
bitmap: 2/6 pages [8KB], 65536KB chunk
Device Boot Start End Blocks Id System
/dev/sda1 1 523 4200966 83 Linux
Partition 1 does not start on physical sector boundary.
/dev/sda2 524 654 1052257+ 83 Linux
Partition 2 does not start on physical sector boundary.
/dev/sda3 655 243201 1948258777+ 83 Linux
Partition 3 does not start on physical sector boundary.
Device Boot Start End Blocks Id System
/dev/sdb1 1 523 4200966 83 Linux
Partition 1 does not start on physical sector boundary.
/dev/sdb2 524 654 1052257+ 83 Linux
Partition 2 does not start on physical sector boundary.
/dev/sdb3 655 243201 1948258777+ 83 Linux
Partition 3 does not start on physical sector boundary.
/dev/md2: UUID="e128e42a-223a-46ea-8d58-d5cd7f090596" TYPE="ext3"
/dev/sda1: UUID="049eebdd-fca4-ddac-1e5f-526a2db4874e"
UUID_SUB="6d5116ae-2357-9686-bb3f-1b1ee68b6bfd" LABEL="billsue1115:0"
TYPE="linux_raid_member"
/dev/sda2: UUID="4d846a1f-7ce5-7cd0-4f03-7e0a06dae47a"
UUID_SUB="9aa0028e-73d6-4a71-237c-b8e865088c4c" LABEL="billsue1115:1"
TYPE="linux_raid_member"
/dev/sda3: UUID="97d78a49-4842-3800-8fde-082d367ca2e9"
UUID_SUB="6e908ddb-349c-a060-68d9-5211dafdb1ac" LABEL="billsue1115:2"
TYPE="linux_raid_member"
/dev/sdb1: UUID="049eebdd-fca4-ddac-1e5f-526a2db4874e"
UUID_SUB="6b8612a2-52e0-5c0e-38a7-2718db79acc4" LABEL="billsue1115:0"
TYPE="linux_raid_member"
/dev/sdb2: UUID="4d846a1f-7ce5-7cd0-4f03-7e0a06dae47a"
UUID_SUB="de6120da-2a5e-5f5a-ab53-eac5df7134d3" LABEL="billsue1115:1"
TYPE="linux_raid_member"
/dev/md0: UUID="c44a2a5e-91f2-43bd-a3e0-2836e3be9074" TYPE="swap"
/dev/md1: UUID="5e00e192-d04e-47dc-89e5-c9f006c77f91" TYPE="ext3"
/dev/sdb3: UUID="97d78a49-4842-3800-8fde-082d367ca2e9"
UUID_SUB="fc5ab547-c3da-4cf7-75d3-92c7ab0fa2bc" LABEL="billsue1115:2"
TYPE="linux_raid_member"
/etc/fstab
UUID=e128e42a-223a-46ea-8d58-d5cd7f090596 / ext3
defaults 1 1
UUID=5e00e192-d04e-47dc-89e5-c9f006c77f91 /boot ext3
defaults 1 2
UUID=c44a2a5e-91f2-43bd-a3e0-2836e3be9074 swap swap
defaults 0 0
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0