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Re: [Qemu-devel] [PATCH v2 1/3] qcow2: introduce compression type featur

From: Markus Armbruster
Subject: Re: [Qemu-devel] [PATCH v2 1/3] qcow2: introduce compression type feature
Date: Tue, 09 Jul 2019 08:15:10 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/26.2 (gnu/linux)

Denis Plotnikov <address@hidden> writes:

> The patch adds some preparation parts for incompatible compression type
> feature to QCOW2 header that indicates that *all* compressed clusters
> must be (de)compressed using a certain compression type.
> It is implied that the compression type is set on the image creation and
> can be changed only later by image conversion, thus compression type
> defines the only compression algorithm used for the image.
> The goal of the feature is to add support of other compression algorithms
> to qcow2. For example, ZSTD which is more effective on compression than ZLIB.
> It works roughly 2x faster than ZLIB providing a comparable compression ratio
> and therefore provide a performance advantage in backup scenarios.
> The default compression is ZLIB. Images created with ZLIB compression type
> are backward compatible with older qemu versions.
> Signed-off-by: Denis Plotnikov <address@hidden>

QAPI schema
Acked-by: Markus Armbruster <address@hidden>

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