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Re: [Qemu-devel] Qemu-img convert with -B

From: Brad Campbell
Subject: Re: [Qemu-devel] Qemu-img convert with -B
Date: Wed, 27 Apr 2011 22:02:22 +0800
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.14) Gecko/20110223 Lightning/1.0b2 Thunderbird/3.1.8 
On 27/04/11 21:56, Kevin Wolf wrote:


When you don't have a backing file, leaving an cluster unallocated means
that it's zero. When you have a backing file, it could be anything. So
if qemu-img convert wanted to save this space, it would have to read
from the backing file and leave the cluster unallocated if it reads as zero.

This is something that qemu-img doesn't do today.
... which would explain the behaviour I'm seeing then. Great, time to dust off my Kernighan & Ritchie I guess. 

Thanks for the explanation.

Regards,
Brad
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