From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Mon, 22 Jul 2013 20:52:37 -0400
From: Kumar amit mehta <gmate.amit@gmail.com>
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Subject: Re: [linux-lvm] lvcreate --thin gives "unknown segment type" error
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To: Zdenek Kabelac <zkabelac@redhat.com>
Cc: linux-lvm@redhat.com

On Mon, Jul 22, 2013 at 10:18:48PM +0200, Zdenek Kabelac wrote:
> It's your backend device used for thinpool data  which doesn't
> support discard. So it fallbacks to  nopassdown behaviour (discard
> is processed only at pool level).

So, it seems that my backend device(of which I've no idea!!) does not 
support discard.
> 
> >I'm invoking these commands on a VM. I do not know, from where these
> >storage were mapped to my VM(were done my some storage admin). However
> 
> Important piece of puzzle - if you want to see TRIM command hits your storage,
> your storage needs to support it ;)
> 
> BTW it's perfectly ok to use thin pool only with nopassdown.
> 
> Zdenek
> 
> 
> NOTE: issue_discard in lvm.conf is not related in any way with
> --discards option for thin pool creation.

Hmm.

Thank you for your time and answering my queries.

!!amit