The number of cylinders for this disk is set to 5221.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
   (e.g., DOS FDISK, OS/2 FDISK)

Command (m for help): p

Disk /dev/xvda: 42.9 GB, 42949672960 bytes
255 heads, 63 sectors/track, 5221 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot      Start         End      Blocks   Id  System
/dev/xvda1   *           1          13      104391   83  Linux
/dev/xvda2              14        2610   20860402+  8e  Linux LVM

Command (m for help): Command (m for help): p
DOS Compatibility flag is not set

Command (m for help): d
Partition number (1-4): 2

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 2
First cylinder (14-5221, default 14):
Using default value 14
Last cylinder or +size or +sizeM or +sizeK (14-5221, default 5221):
Using default value 5221

Command (m for help): t
Partition number (1-4): 2
Hex code (type L to list codes): 8e
Changed system type of partition 2 to 8e (Linux LVM)

Command (m for help): p

Disk /dev/xvda: 42.9 GB, 42949672960 bytes
255 heads, 63 sectors/track, 5221 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot      Start         End      Blocks   Id  System
/dev/xvda1   *           1          13      104391   83  Linux
/dev/xvda2              14        5221   41833260   8e  Linux LVM

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 16: Device or resource busy.
The kernel still uses the old table.
The new table will be used at the next reboot.
Syncing disks.

pvresize -v /dev/xvda2
    Using physical volume(s) on command line
    Archiving volume group "VolGroup00" metadata (seqno 3).
    Resizing physical volume /dev/xvda2 from 636 to 1276 extents.
    Resizing volume "/dev/xvda2" to 83666136 sectors.
    Updating physical volume "/dev/xvda2"
    Creating volume group backup "/etc/lvm/backup/VolGroup00" (seqno 4).
  Physical volume "/dev/xvda2" changed
  1 physical volume(s) resized / 0 physical volume(s) not resized

pvs
  PV         VG         Fmt  Attr PSize  PFree
  /dev/xvda2 VolGroup00 lvm2 a-  39.88G 20.00G

lvextend -l +100%FREE /dev/VolGroup00/LogVol00

lvs
  LV       VG         Attr   LSize  Origin Snap%  Move Log Copy%  Convert
  LogVol00 VolGroup00 -wi-ao 37.84G
  LogVol01 VolGroup00 -wi-ao  2.03G

resize2fs /dev/mapper/VolGroup00-LogVol00

df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
                       37G  4.5G   31G  13% /
/dev/xvda1             99M   22M   73M  24% /boot
tmpfs                 2.0G     0  2.0G   0% /dev/shm
任务完成

遇到的问题
linux系统为centos7 时， 用 resize2fs 命令出现报错 resize2fs: Bad magic number in super-block while trying to open
xfs_growfs /dev/root_vg/root 用 xfs_growfs 代替命令 resize2fs