17.06.2021 22:51, Vladimir Sementsov-Ogievskiy wrote:
Recently we added support of zstd to qcow2 format, as zstd seems to be
better than zlib in general, and which is important (as qcow2
compression used mostly for backups) compressed writes are faster with
zstd.
Let's add a build option to use zstd by default.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
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Hi all! We want to use zstd as a default compression type for newly
created qcow2 images in upcoming Virtuozzo 8.
I am not sure, how much the community interested in such option,
probably I should just keep a downstream-only patch changing the
default.
But if you like it, I'd be happy to only set new config option in our
qemu build instead of maintaining extra downstream-only patch :)
So, it's an RFC. I also can split the patch so that refactoring of
qcow2_co_create() go in a separate preparation patch.
Another RFC question, shouldn't we move to zstd by default in upstream
too?
First: the biggest difficulty with zstd as default is updating all iotests to
work in such conditions. I'm working on this now and hope to post series soon,
which just improves iotests to support IMGOPTS='compression_type=zstd'. That's
a first step which is good anyway and don't change any default.
Next: I have a doubt now. Maybe, better way of having alternative default in
downstream project is introcuducing a kind of configuration file for Qemu? Qemu
will parse it if exist, and we can ship such a file in rpm package. Something
like /etc/qemu.conf. Any thoughts? Did something like this ever considered?
Benefit of configuration file vs build options is obvious: you can change a
default without recompiling.
--
Best regards,
Vladimir
