[linux-lvm] Converting my Root file system to LVM [last

[Mark van Walraven]

On Tue, May 29, 2001 at 09:12:17AM +0000, Heinz J. Mauelshagen wrote:
> > When/if you do this, please consider systems with root on LVM.  Building a
> > ramdisk and pivoting root to that seems clumsy at best.  Perhaps vgchange
> > could have an option to request a metadata flush, which is deferred until
> > the relevant volumes are closed?
> 
> Mark,
> I am not sure if I get you right here...

Probably because I didn't make sense.  I was thinking that the metadata
write could be scheduled to pend until all LVs were closed.  But that
doesn't help, because root is never unmounted ...

> But in case a metadata write at VG deactivation is needed in the future,
> the update would take place *before* the try to unload it from the kernel.

Do you mean that the metadata write might be a separate operation to
deactivation, permitted even before the LVs were closed?

> This is a valid sequence IMO, because reasons for unloadable metadata are

s/unloadable/non-unloadable/ ?

> open LVs caused by hanging applications (database systems et al.) or unmounted
> filesystems which don't influence the correctness of the LVM metadata anyway.

How about filesystems mounted read-only?  My current shutdown sequence goes:

	/etc/rc6.d/S40umountfs:
		swapoff -a
		umount -f -a -r
		mount -n -o remount,ro /

	/etc/rc6.d/S50lvm:
		/sbin/vgchange -A n -a n

	/etc/rc6.d/S90reboot:
		reboot -d -f -i

Which doesn't work because root is on an LV.  But even if the lvm
shutdown script could write the metadata while root was open, the VGDA
would still end up recording an active VG and open LV, unless you had
something analogous to "re-mount read-only" for LVs and VGs.

Regards,

Mark.