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Re: Sharing LVM storage

On Wed, 15 Apr 2015 09:55:10 +0300
Reco <recoverym4n@gmail.com> wrote:

>  Hi.
> On Wed, Apr 15, 2015 at 08:41:07AM +0200, Petter Adsen wrote:
> > > > I just want to try it out to see how it works, it's not
> > > > something I need by any stretch of the imagination, so there's
> > > > a limit to how far down that rabbit-hole I want to go.
> > > 
> > > As long as you don't forget to run lvscan on partner node after
> > > doing basically anything with LV on main node - you should be OK.
> > > 
> > > But just to be on the safe side - don't export PV via iSCSI.
> > > Export LVs.
> > 
> > May I ask why, so I don't mess anything up? I was thinking of
> > exporting maybe my VM VG, so that all LV's for VM's were available
> > to both machines. Or just the device itself.
> That's the main reason. Creating PV-via-iSCSI configuration from the
> scratch is simple. It's maintaining it (or worse - changing it) is
> complex.
> For example, imagine the need to migrate all LVs from one PV to
> another. Without downtime, of course. Is it doable - yes. Is it
> simple - no.

In my setting, that is quite simply not going to ever happen. I have a
separate disk with one PV on it, devoted entirely to VM's. But I do see
your point, if I ever were to use it in a production system. Right now,
downtime only means that one of my personal toys is broken :)

> Besides, there's a *small* matter of backups, and in cases such as


> this I prefer straightforward approach. I.e. there's "storage" host,
> and there are "VM" hosts. "Storage" host provides LVs as /dev/sd*
> devices to "VM" hosts *and* manages backups. "VM" hosts merely do
> their VM thing.

I see, thank you. Well, that sort of fits in with my setup, too, except
that the VM disk is not in the storage server, it is in the fastest
machine I have, with the most cores available to run VMs.

It's just a toy project, anyhow, but it's best to learn good practices.


"I'm ionized"
"Are you sure?"
"I'm positive."

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