[mdlug] More new hard drive details

[Jonathan Billings]

On Thu, Jan 15, 2009 at 03:07:37PM -0500, Aaron Kulkis wrote:
> Where is the current Linux LVM putting the LVM data?
> I can't see it being stored in the boot sectors, because there
> just plain old isn't enough space there.

I believe there is a metadata area for each physical volume in LVM,
which is stored after the disk label or near the beginning of the
partition, depending on whether you're using whole-device volumes or
volumes on DOS partitions.  The PV metadata starts 5 sectors in.

By default, there is a copy of the metadata for the entire volume
group stored in each physical volume, and each physical volume is
referred to by UUID, so device naming doesn't matter.  This redundancy
can make metadata updates rather slow, but the alternative is what
you've descibed earlier.

Certainly LVM2 adds another layer of indirection.  However, it's
safe and gives you flexibilities with resizing, striping and moving
volumes that you don't get with using DOS partitions.

Eventually, there will probably be ZFS (or a zfs-like clone) for linux
which will make LVM2 less useful.  

-- 
Jonathan Billings <billings at negate.org>