[linux-lvm] expanding on LVM2

Sharad Tiwari sharad.tiwari at wipro.com
Wed Apr 2 05:13:03 UTC 2003

Hi all,
	This is a plain text mail (no html) ... hope it does reach you
all ...

> >LVM(2) handles that by using physical volume uuids (as you mention
> >below).
> >
> >Device paths can change that way and LVM will stil find the disks and
> >assemble them correctkly into volume groups.

Will the PV uuid be unique ... I mean to say is there a possibility of
two nodes issuing same PV uuid (when working independently)

If I connect multiple hard disks to a node, take a partition on a node
(say /dev/hdd1) and make a physical volume out of it, and then connect
the hard disk as a primary slave( /dev/hdb) and then run a pvdisplay ,
the physical volume does show the device name as /dev/hdb but cribs
about not finding /dev/hdd ... can this be avoided.

One more question I had was, How exactly is a raw device operation
request handled in LVM.

I was going through the code and did not find any character device
interface(for raw device operations) ... but again dd worked on the
logical volume .. so I am wondering how dd worked in the absebce of a
raw device operation support.

> >For 'pricate' volume group the situation is a failover situation.
> >You need have a design which makes sure that only one node can have
> >volume group active at any given time and if that one fails,
> >the failure, make sure the the failed node can't get back to life
(which > >will cause strange problems) and take the VG over at an
arbitrary other node.

Two questions I have on this are :

What is the failover mechanism being followed in LVM2 ???
I found out that when I do a vgcreate, a file called vgcreate.tmp is
created which is later renamed as vgcreate, now what happens if the node
happens to crash just after these entries are written onto the hard

If I happen to change the configurations where are they stored  ??

Thanks for the help,


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