[linux-lvm] shift PV from disk to raid device?

Stuart D. Gathman stuart at bmsi.com
Tue Dec 9 21:03:36 UTC 2008

On Tue, 9 Dec 2008, Kai Schaetzl wrote:

> > The solution to this problem is to create the raid device with a
> > superblock format of 1.1 or 1.2 (aka, -e 1.1 or -e 1.2).
> Is this an option to mdraid? mdadm --create --help doesn't show me this 
> option. Might mdadm-2.6.4-1.el5 on 5.2 be too old? Or is this an option to 
> fdisk/sfdisk?

I don't think changing the raid superblock will help.  I generally
prefer having the superblock at the end - there are times when you
*do* want sda3/sdb3 to alias md3:

 o many versions of grub will not install on md? - you have to unmount /boot,
 break mirror, mount sd? on /boot, install grub, unmount /boot, mount md? on
 /boot again, add back mirror copy of /boot.

 o Also, when recovering a system, it is helpful to be able to mount a
 partition directly, without setting up the raid devices.  I've had customers
 remove a mirror copy and mail me the disk.  I can then mount the filesystems
 directly, while they keep operating.

The key is breaking the aliasing and copying the data to a proper md? PV.

	      Stuart D. Gathman <stuart at bmsi.com>
    Business Management Systems Inc.  Phone: 703 591-0911 Fax: 703 591-6154
"Confutatis maledictis, flammis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.

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