Multiple Logical Groups out of a Physical Volume

Hi_This_is_Dev · 04-26-2010, 04:31 PM

How to create multiple Logical Groups out of a single Physical Volume?

Here is the Physical Volume I have created:

Code:

# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sda9
  VG Name               myVG1
  PV Size               54.88 MB / not usable 2.88 MB
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              13
  Free PE               11
  Allocated PE          2
  PV UUID               bon4Ao-vmgC-aP1h-EC9X-w3tN-YXNu-0N2dAw

This is how I am creating a Logical Group out of the above Physical Volume:

Code:

# vgcreate myVG1 -s 4m /dev/sda9

Display:

Code:

# vgdisplay
  --- Volume group ---
  VG Name               myVG1
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  5
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               1
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               52.00 MB
  PE Size               4.00 MB
  Total PE              13
  Alloc PE / Size       2 / 8.00 MB
  Free  PE / Size       11 / 44.00 MB
  VG UUID               O6ljYC-bflz-EUTd-nf34-8gYe-Fh39-Bh3cOg

But I am unable to create one more Logical Group out of this Physical Volume.

Can we accomplish it? Or do we always extend our current Logical Group to utilise the available space of a Phyiscal Volume?

samborambo · 04-26-2010, 06:42 PM

Physical Volumes (PVs) are allocated to whole devices only. VGs require at least one whole PV. If you want more than on VG you need a PV for each. The solution is to partition sda with 2 partitions. You can have a maximum of 16 partitions on one physical device using logical partitions.

Although the whole point of using LVM is that you don't need partitions. Wouldn't it be simpler if you convert your other partitions to LVs and just use the entire drive as a PV and VG?

Sam.

Hi_This_is_Dev · 04-26-2010, 08:31 PM

Quote:

Originally Posted by samborambo

Physical Volumes (PVs) are allocated to whole devices only. VGs require at least one whole PV. If you want more than on VG you need a PV for each. The solution is to partition sda with 2 partitions. You can have a maximum of 16 partitions on one physical device using logical partitions.

Although the whole point of using LVM is that you don't need partitions. Wouldn't it be simpler if you convert your other partitions to LVs and just use the entire drive as a PV and VG?

Sam.

Yes, I think your point is right. I confirmed from some UNIX Admin here in my project / office and he also told me that only one VG can be created out of a PV.

Actually, one of my colleagues here told me that we could achieve what I asked in the question, but that is not practical.

Thanks for your views!