From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dmitry Olenin <dolenin@parallels.com>
Subject: Re: How to remount btrfs without compression?
Date: Wed, 9 Nov 2011 17:03:39 +0900
Message-ID: <4EBA33DB.2070409@parallels.com>
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On 11/09/2011 04:48 PM, Lubos Kolouch wrote:
> Sorry for possibly OT question - when I have historical btrfs system
> mounted with zlib compression,
>
> can I remount it with lzo ? What will happen? Will the COW be broken
> and the files taking duplicate space? Or will the Universe explode and
> be replaced with something even more bizzare?

Hello Lubos
If you have a kernel that supports lzo (don't quite remember when it got 
in), why can't you?
Absolutely nothing will happen, and only the new/updated files will be 
with lzo compression. You can remount on the fly switching b/w the two 
compression options without any problems.