一、SWAP分割槽大小設定參考：

4G以內的實體記憶體，SWAP 設定為記憶體的2倍。

4-8G的實體記憶體，SWAP 等於記憶體大小。

8-64G 的實體記憶體，SWAP 設定為8G。

64-256G實體記憶體，SWAP 設定為16G。

二、擴充或縮小SWAP分割槽：

[root@node1 ~]# swapon -s
Filename                                Type            Size    Used    Priority
/dev/dm-1                               partition       1048572 0       -1
[root@node1 ~]# free -m
             total       used       free     shared    buffers     cached
Mem:          1861        402       1458          1         30        136
-/+ buffers/cache:        235       1626
Swap:         1023          0       1023

[root@node1 ~]# swapoff /dev/mapper/vg_node1-lv_swap
[root@node1 ~]# free -m
             total       used       free     shared    buffers     cached
Mem:          1861        402       1459          1         30        136
-/+ buffers/cache:        235       1626
Swap:            0          0          0

[root@node1 ~]# fdisk -l

Disk /dev/mapper/vg_node1-lv_swap: 1073 MB, 1073741824 bytes
255 heads, 63 sectors/track, 130 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

[root@node1 ~]# lvextend -L 2G /dev/mapper/vg_node1-lv_swap
  Size of logical volume vg_node1/lv_swap changed from 1.00 GiB (256 extents) to 2.00 GiB (512 extents).
  Logical volume lv_swap successfully resized

最後要使用resizefs2命令重新載入邏輯卷的大小才能生效
resize2fs 

/dev/mapper/vg_node1-lv_swap

[root@node1 ~]# free -m
total used free shared buffers cached
Mem: 1861 403 1458 1 30 136
-/+ buffers/cache: 236 1625
Swap: 2047 0 2047

格式化swap分割槽命令：　　

mkswap /dev/mapper/vg_node1-lv_swap