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Date: Tue, 22 Apr 2008 12:28:10 -0400
From: Charles Marcus <CMarcus@Media-Brokers.com>
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Subject: Re: [linux-lvm] Snapshot question...
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To: LVM general discussion and development <linux-lvm@redhat.com>

On 4/22/2008, Stephane Chazelas (stephane.chazelas@emerson.com) wrote:
> When you read from your original volume (that has been changed
> to be of "snapshot-origin" type), you actually read from the
> "real" volume (the original version of the original volume), but
> when you write to it, the system makes sure that unless it has
> been done already, the block you're modifying are being copied
> first from the "real" volume to COW volume before being modified
> in the "real" volume.
> 
> So to sum up, the "snapshot" volume you are creating is a
> "virtual" volume that is a front end to both the snapshot
> storage volume ("COW") and the original real volume ("real").
> 
> Hope this clarifies a bit,

Thanks for trying, but no, that just made my head hurt...

;)

Seriously... if the snapshot volume that I'm creating is a front end to 
BOTH, when I back it up, I guess LVM just 'knows' that I mean to backup 
the 'original'?

Is there a graphical outline of how this works? I seem to do better with 
visualizations...

-- 

Best regards,

Charles