Resize the CentOS LVM inside VM from a secondary virtual hard disk

Question

Requirement:
Airwave installed on a VM, with a secondary virtual hard disk.
we have a KB "Resizing the centOS LVM inside VM", is only useful if we have one hard disk for that VM instance.
https://arubanetworkskb.secure.force.com/pkb/articles/FAQ/Resizing-CentOS-LVM-inside-VM
However,  This KB will be helpful in the scenario's where VM Administrators has to create a secondary virtual Hard disk, instead of increasing the disk space for current hard disk (could be for any reason for example: he cannot increase the disk space for the same disk as the pool that provides space to that disk has no space etc..).
Solution:
In this case, when we have added a secondary virtual hard disk, when we do # fdisk -l, we will see the secondary disk as /dev/sdb  as shown below:
[root@localhost mercury]# fdisk -l
Disk /dev/sda: 42.9 GB, 42949672960 bytes
255 heads, 63 sectors/track, 5221 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: 0x000650f3
   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          13      102400   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2              13        5222    41839616   8e  Linux LVM
Disk /dev/sdb: 17.2 GB, 17179869184 bytes
255 heads, 63 sectors/track, 2088 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
Disk /dev/mapper/VolGroup00-LogVol01: 4294 MB, 4294967296 bytes
255 heads, 63 sectors/track, 522 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
Disk /dev/mapper/VolGroup00-LogVol00: 38.5 GB, 38520487936 bytes
255 heads, 63 sectors/track, 4683 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
And this is the # df -h, command output, before the LVM extension:
[root@localhost mercury]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
                       36G   11G   23G  32% /
tmpfs                 3.7G     0  3.7G   0% /dev/shm
/dev/sda1              97M   37M   56M  40% /boot
We need to extend the sdb disk space to VG group to combine to use the disk space as shown below in the configuration:
Configuration:
1. First, we need to create a partition in /dev/sdb
[root@localhost mercury]# fdisk /dev/sdb
# n {new partition}
# p {primary partition}
# 1 {select partition number, by default 3 is the next available}
# use the default cylinder values for First and last
# t {select partition id we just made (1)}
# 8e {Linux LVM partition}
# p {print. the new device should be described as Linux LVM}
# w {write to memory}
2. We need pv reate /dev/sdb1:
[root@localhost mercury]# pvcreate /dev/sdb1
3. Execute the command to extend the VG to sdb1:
[root@localhost mercury]# vgextend VolGroup00 /dev/sdb1
4. Enter the command to extend the LV to sdb1:
[root@localhost mercury]# lvextend /dev/VolGroup00/LogVol00 /dev/sdb1
5. Resize the VG:
[root@localhost mercury]# resize2fs /dev/VolGroup00/LogVol00
Done.
Verification
Now look at the # df -h, output, which will be different:
[root@localhost mercury]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
                       52G   11G   38G  22% /
tmpfs                 3.7G     0  3.7G   0% /dev/shm
/dev/sda1              97M   37M   56M  40% /boot

Answer 1

Hi Eric,
"My first thought was to do is reduce the drive, which I know cannot be done. I then thought to convert the disk but it consumes the whole of the dynamic potential, which somehow is a maximum of 2TB."
Yes , we can not get the disk space less  than 2TB .
As a workaround , you can try the following steps :
1) defrag the volume  in VM , after that shutdown the VM
2) use "edit disk" in hyper-v manager to compact the VHD file
3) start that VM then shrink the volume that the disk space is larger than the VM needs in disk manager
This may limits the expansion accordingly .
Hope it helps
Best Regards
Elton JI
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