[linux-lvm] lsm space giveth and space taketh away: missing space?

Stuart D. Gathman stuart at bmsi.com
Thu Sep 2 03:44:08 UTC 2010

On Wed, 1 Sep 2010, Linda A. Walsh wrote:

> lvresize /dev/Backups/Backups -L +3.15G
>  Rounding up size to full physical extent 3.15 GB
>  Extending logical volume Backups to 10.91 TB
>  Logical volume Backups successfully resized
> Um...HELLO?  Extending to 10.91?  But it was at 10.91!

3.15G is not significant compared to 10.91TB.  You know the saying, 
"A billion here and a billion there, and pretty soon you're talking
about real storage."

> So why does parted show a 12TB disk while lvm shows only a 10.91T
> disk and why did lvm show 3.15G free when it wasn't really there?

12.0 TeraBytes (12*10^12) ~= 10.91 TibiBytes (10.91*2^40) to 4 decimals.  The
3.15G was there, you added it to your LV (but you still need to resize the
filesystem).  10.91*2^40 + 3.15*2^30 ~= 10.91*2^40 to 4 decimals.

> How do I get my 1.09T back from lvm?  That seems like awfully
> high for an overhead number for lvm.  I'd expect more like "0.09T".


	      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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