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Re: [Libvir] PATCH: 12/16: logical volume backend



On Tue, Feb 19, 2008 at 12:46:28PM +0000, Daniel P. Berrange wrote:
> On Tue, Feb 19, 2008 at 03:43:11AM -0500, Daniel Veillard wrote:
> > > +
> > > +        /*
> > > +         * LVM requires that the first 512 bytes are blanked if using
> > > +         * a whole disk as a PV. So we just blank them out regardless
> > > +         * rather than trying to figure out if we're a disk or partition
> > > +         */
> > 
> >   is it really 512 or the block size on the device used ? But 512 is
> > probably sufficient for LVM to consider it cleared, just wondering ...
> 
> The 'pvcreate' man page explicitly says the first sector
> 
> <quote>
>    For whole disk devices only the partition table must be erased, 
>    which will effectively destroy all data on that disk.  This can 
>    be done by zeroing the  first  sector with:
> 
>        dd if=/dev/zero of=PhysicalVolume bs=512 count=1
> </quote>
> 
> So 512 is fine for MSDOS partition tables at least.

  Ahh, the legacy :-) thanks for the explanations !

Daniel

-- 
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Daniel Veillard      | virtualization library  http://libvirt.org/
veillard redhat com  | libxml GNOME XML XSLT toolkit  http://xmlsoft.org/
http://veillard.com/ | Rpmfind RPM search engine  http://rpmfind.net/


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