[Ocfs2-users] OCFS2 and LVM2

[Alexei_Roudnev]

You can experiment. Sometimes you ca restart LVM.

But yes, I recommend to keep 2 different run levels, if you have not console
access (why dont use serial console or IP KVM? New servers have usually
remote access option, such as DRAC card in DELLS or RIB card in Compaques):

- rl.3 - basic system without LVM (turn it off), ocfs and your applications.
Just network, basic mounts,
ssh.
- rl.5 - lvm, ocfs and applications.

Be careful. I recommended to restart, because you never can be sure, after
restarting lvm and so on, how lvm see new volume allocation now.
That's why I recommended to reboot other nodes in all cases. Of course, you
can find a working solution without the reboot (it do exists for sure),
but again, be very careful, because if you start running OCFSv2 with 2
servers, 1 see the whole volume and other - 90% of this volume, results can
be devastating.


----- Original Message ----- 
From: "Gerry Reno" <greno at verizon.net>
To: "Alexei_Roudnev" <Alexei_Roudnev at exigengroup.com>
Cc: <Ocfs2-users at oss.oracle.com>
Sent: Monday, February 26, 2007 12:29 PM
Subject: Re: [Ocfs2-users] OCFS2 and LVM2


> Alexei_Roudnev wrote:
> > You must understand how LVM2 works. It is all STATIC system, so it
ALWAYS
> > can be used in cluster until you don't change metadata. Think about LVM
as
> > about partitions on the disk - you can use partitions with OCFS, so you
can
> > use LVM with OCFS (but you can't change partitions online).
> >
> > You can create LVM2 volumes using one node, then restart other nodes
(and
> > let them to scan disks) and they will see these volume(s). Then you can
use
> > it as you wish.
> > But to change volumes, you will:
> > - stop all nodes but one
> > - update LVM2 volume on this node
> > - start other nodes
> >
> > So, you CAN use LVM2 but you CAN NOT change metadata online while
cluster
> > have more than 1 running node (running node - running OS, stopping OCFS
is
> > not enough).
> >
> > PS. You don't need to create volumes on a few nodes. What you must do is
to
> > create volumes on ONE node and run vgscan or (boot.lvm start) on all
other
> > nods (so they recognize your volumes).
> >
> Ok, this is a little better than I thought having to make the LVM2
> changes on just one node.  So you are saying I must shutdown the other
> nodes completely not just stop OCFS2?  That is going to require console
> access to each machine.  Could I just put them in another init level?
> Something that we could do remotely.
>
> > I recommend to look onto EVMS integrated with OCFSv2 (by SuSe), as a
> > possible alternative.
> >
> >
> I will look at this.
>
> Thanks,
> Gerry
>
>
>