Is this rule is true?

[Ashraf_1]

Is it true that there is a rule said " for any single physical volume their should be only one dedicated volume group and you can't have more than one volume group on that physical volume".

Please confirm if this is true or if there is a way of doing it.

Thanks & Regards,
Ashraf

[Roger Baptiste]

Yes, it is true. A physical volume (disk/lun as seen in
the ioscan ouput) can belong
to only ONE volumegroup.

That is how the VG layout is
structured. Physical volumes
are grouped together under
one VG and then the VG is
sliced into different LV's.
There LV's can use space on
all the PV's of the VG.

-raj

[Joseph C. Denman]

My answer would be TRUE.

But you can have several pv in one vg.


...jcd...

[Volker Borowski]

Yes.

Thinking of a physical volume as a single disk attached to the system, you can not put this disk into two volume groups.

If you have storage systems in between, which offer to define logical units to be seen from the OS as physical volumes, it might be posible, that two volumegroups reside on the same physical disk, but in this case this disk shows up as two physical volumes to the OS.

Hope this helps
Volker

[James R. Ferguson]

Hi:

Yes, a physical volume (disk) can belong to only one logical volume.

The man pages ('man 7 lvm') for LVM have a good, short overview of basic concepts.

Regards!

...JRF...

[Mike Hassell · Accepted solution]

Ashraf,

I agree with the others, that each physical disks are gathered into a specific volume group, here is some documentation that supports this:

http://docs.hp.com/hpux/onlinedocs/B2355-90684/B2355-90684.html

-> Section 7 -> L -> LVM

"Unlike earlier arrangements where disks were divided into fixed-sized sections, LVM allows the user to consider the disks, also known as physical volumes, as a pool (or volume) of data storage, consisting of equal-sized extents. The default size of an extent is 4 MB.

An LVM system consists of arbitrary groupings of physical volumes, organized into volume groups. A volume group can consist of one or more physical volumes. There can be more than one volume group in the system. Once created, the volume group, and not the disk, is the basic unit of data storage. Thus, whereas earlier one would move disks from one system to another, with LVM, one would move a volume group from one system to another. For this reason it is often convenient to have multiple volume groups on a system."

Hope that helps.

-Mike

[Deshpande Prashant]

YES
A physical volume can be part of only one volume group.
You can create multiple logical volumes (in same VG) on single physical disk.

Thanks.
Prashant.

[Victor_5]

Yes.

One PV only can under one VG at one time.

Shawn

[harry d brown jr]

It's true and false. Wow! A physical disk, and I'm talking about the actual hardware, not what is served up to the host, can be "sliced". Look at any EMC or autoraid configuration, where a physical disk can be "
carved up into slices. So the documentation should read "PSEUDO PHYSICAL DISKS".


live free or die

[Patrick Wallek]

Harry makes a good point about disk arrays, and their ability to slice the disks into pieces.

When you think of a physical disk, think of it as that (be it an actual JBOD disk or EMC hypervolume, or other array slice) which is referenced by a device file (/dev/[r]dsk/c?t?d?).

Each disk device file can only belong to one Volume Group (VG). Each VG can, and usually does, contain more than one disk device, thus the "group" part of volume group.

I hope this makes sense.

[Wodisch]

Actually, it is even more of a Yes AND No:
For LVM the answer is obviously: NO!
But AFAIK for the (new) VxVM (Veritas Volume Manager) the answer is: YES!

Glad to contribute to the confusion ;-)

Wodisch