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Date: Mon, 15 Jul 2013 10:33:06 +0200
From: Zdenek Kabelac <zdenek.kabelac@gmail.com>
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Subject: Re: [linux-lvm] Mirroring to a thin volume
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To: LVM general discussion and development <linux-lvm@redhat.com>
Cc: Raymond Jennings <shentino@gmail.com>

Dne 15.7.2013 07:46, Raymond Jennings napsal(a):
> Is there a way to hot-convert a live volume to thin provisioning?
>
> I was thinking of doing this:
>
> 1.  Create a thin volume
> 2.  Have it mirror the linear volume
> 3.  Break the linear mirror
> 4.  Run an fs discard on the thin volume

There is planned feature 'merge' of any LV into thin pool - so you would
be able to turn your LV into thin volume (but likely there will not a be a way 
to split such thin-LV back to non-thin LV anytime soon).

In the upstream git there is already support for 'external origin'
where you could use some LV as a source for 'unprovisioned' blocks
which is something like snapshot of LV where modified blocks
are put into thin pool -  but this feature has some limitation -
i.e. for now you cannot 'merge' modified blocks back to external origin.

I guess mirror construction currently only supports PVs - so
you would need to use 'stacked' VG - there is planned better support for 
stacking of volumes in a VG - but it's not so easy as it might look.

Zdenek