[linux-lvm] LVM2 on-disk layout

Stuart D. Gathman stuart at bmsi.com
Mon Jan 5 18:49:45 UTC 2009

On Mon, 5 Jan 2009, Tejas Sumant wrote:

> I have few questions on lvm2 layout.
> 1) Why array of MDA (metadata area) is required? Isnt single MDA sufficient?

It is not *required*, there is an option for only 1 MDA.  The extra
copies are for backup.  If main MDA gets wiped, and you don't have a backup
on a separate volume (I keep one in boot partition), then you will be glad
of the backup.

> 2) Which MDA is current?

There should be a counter in each MDA to determine most current.  Also
each MDA has a CRC to detect partial updates, and discourage manual

> 3) Why the metadata inside MDA wraps around, instead of the offset
> pointing to the start of metadata?

Someone else?

	      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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