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Re: Clarification regarding new qemu-img convert --target-is-zero flag


From: Eric Blake
Subject: Re: Clarification regarding new qemu-img convert --target-is-zero flag
Date: Wed, 10 Jun 2020 10:48:52 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0

On 6/10/20 10:42 AM, David Edmondson wrote:
On Wednesday, 2020-06-10 at 18:29:33 +03, Sam Eiderman wrote:

Excuse me,

Vladimir already pointed out in the first comment that it will skip
writing real zeroes later.

Right. That's why you want something like "--no-need-to-zero-initialise"
(the name keeps getting longer!), which would still write zeroes to the
blocks that should contain zeroes, as opposed to writing zeroes to
prepare the device.

Or maybe something like:

qemu-img convert --skip-unallocated

which says that a pre-zeroing pass may be attempted, but it if fails, only the explicit zeroes need to be written rather than zeroes for all unallocated areas in the source (so the resulting image will NOT be an identical copy if there were any unallocated areas, but that the user is okay with that).

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org




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