硬盘不够用了，里面在大量的小文件，cp或rsync都非常慢。

开始又没有做LVM,现在要拿两个大硬盘做LVM，去换这个硬盘。

怎么COPY数据是最快的？

我的想法是用DD：

比如现在的硬盘是73G的,/dev/sdb1

拿两块147的做LVM,/dev/mapper/VolGroup00-LogVol01

我现在：

dd if=/dev/sdb1 of=/dev/mapper/VolGroup00-LogVol01

这样是否可行？

/dev/mapper/VolGroup00-LogVol01比/dev/sdb1大，会不会有问题？

下面是操作步骤，测试结果说明方案可行：

有三块硬盘:

fdisk -l
Disk /dev/sdb: 1073 MB, 1073741824 bytes
Disk /dev/sdc: 1610 MB, 1610612736 bytes
Disk /dev/sdd: 2147 MB, 2147483648 bytes

先分区：

/dev/sdb1为linux分区。 /dev/sdc1和/dev/sdd为linux lvm分区。

格式化并复制一些测试文件进去

mkfs -t ext3 /dev/sdb1
mkdir /sdb1
mount /dev/sdb1 /sdb1
cp -rf /* /sdb1

磁盘占用：

[root@rhel4 /]# df -h
Filesystem            Size Used Avail Use% Mounted on
/dev/sda3             6.8G 1.9G 4.7G 28% /
/dev/sda1              99M   12M   82M 13% /boot
none                  252M     0 252M   0% /dev/shm
/dev/sdb1            1004M 1004M     0 100% /sdb1

建立lvm:

[root@rhel4 /]# pvcreate /dev/sdc1
Physical volume “/dev/sdc1” successfully created
[root@rhel4 /]# pvcreate /dev/sdd1
Physical volume “/dev/sdd1” successfully created

[root@rhel4 /]# vgcreate vg1 /dev/sdc1 /dev/sdd1
/dev/cdrom: open failed: No medium found
Volume group “vg1” successfully created

[root@rhel4 /]# vgdisplay
— Volume group —
VG Name               vg1
System ID            
Format                lvm2
Metadata Areas        2
Metadata Sequence No 1
VG Access             read/write
VG Status             resizable
MAX LV                0
Cur LV                0
Open LV               0
Max PV                0
Cur PV                2
Act PV                2
VG Size               3.49 GB
PE Size               4.00 MB
Total PE              893
Alloc PE / Size       0 / 0  
Free PE / Size       893 / 3.49 GB
VG UUID               sE9vmk-Kuma-ITAI-irkv-qyey-G1cl-mVilAy

[root@rhel4 /]# lvcreate -L 3.48G -n lv1 vg1
Rounding up size to full physical extent 3.48 GB
Logical volume “lv1” created
[root@rhel4 /]# lvdisplay
— Logical volume —
LV Name                /dev/vg1/lv1
VG Name                vg1
LV UUID                8zkO0q-mmYv-Km4y-aw4q-5BAw-H7hI-cKtrK7
LV Write Access        read/write
LV Status              available
# open                 0
LV Size                3.48 GB
Current LE             891
Segments               2
Allocation             inherit
Read ahead sectors     0
Block device           253:0

建立文件系统：

[root@rhel4 /]# mkfs -t ext3 /dev/vg1/lv1

[root@rhel4 /]# mkdir /lv1
[root@rhel4 /]# mount /dev/vg1/lv1 /lv1
[root@rhel4 /]# df -h
Filesystem            Size Used Avail Use% Mounted on
/dev/sda3             6.8G 1.9G 4.7G 28% /
/dev/sda1              99M   12M   82M 13% /boot
none                  252M     0 252M   0% /dev/shm
/dev/sdb1            1004M 1004M     0 100% /sdb1
/dev/mapper/vg1-lv1   3.5G   39M 3.3G   2% /lv1

卸下/dev/sdb1 及/dev/mapper/vg1-lv1：

[root@rhel4 /]# umount /dev/sdb1
[root@rhel4 /]# umount /dev/mapper/vg1-lv1

把/dev/sdb1复制到/dev/mapper/vg1-lv1：

[root@rhel4 /]# dd if=/dev/sdb1 of=/dev/mapper/vg1-lv1 bs=8MB
133+1 records in
133+1 records out

bs是块大小，这里是8MB，块越大速度越快，只要内存够用。这里花了30秒就跑完了。测试在vmware进行，内存是512M

挂上LVM，看下：

[root@rhel4 /]# mount /dev/mapper/vg1-lv1 /lv1
[root@rhel4 /]# df -h
Filesystem            Size Used Avail Use% Mounted on
/dev/sda3             6.8G 1.9G 4.7G 28% /
/dev/sda1              99M   12M   82M 13% /boot
none                  252M     0 252M   0% /dev/shm
/dev/mapper/vg1-lv1 1004M 1004M     0 100% /lv1
[root@rhel4 /]# ls /lv1/
bin boot dev etc home initrd lib lost+found media misc mnt opt proc usr

里面内容都在。就是最大容量也变成和/dev/sdb1一样了，我们需要扩展一下：

RHEL 4: ext2online /dev/mapper/vg1-lv1

RHEL 5: resize2fs -p /dev/mapper/vg1-lv1

[root@rhel4 /]# ext2online /dev/mapper/vg1-lv1
ext2online v1.1.18 - 2001/03/18 for EXT2FS 0.5b
[root@rhel4 /]# df -h
Filesystem            Size Used Avail Use% Mounted on
/dev/sda3             6.8G 1.9G 4.7G 28% /
/dev/sda1              99M   12M   82M 13% /boot
none                  252M     0 252M   0% /dev/shm
/dev/mapper/vg1-lv1   3.5G 1005M 2.3G 31% /lv1

OK，完成复制。以上在centos4及centos 5上测试通过