From: Kevin Wolf <kwolf@redhat.com>
To: "Wang, Wei W" <wei.w.wang@intel.com>
Cc: "lersek@redhat.com" <lersek@redhat.com>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"qemu-block@nongnu.org" <qemu-block@nongnu.org>,
"mreitz@redhat.com" <mreitz@redhat.com>
Subject: Re: Question on Compression for Raw Image
Date: Tue, 20 Oct 2020 10:00:51 +0200 [thread overview]
Message-ID: <20201020080051.GA4452@merkur.fritz.box> (raw)
In-Reply-To: <516589845d6f42d0b00784d16b59b5dc@intel.com>
Am 20.10.2020 um 03:31 hat Wang, Wei W geschrieben:
> Hi,
>
> Does anyone know the reason why raw-format.c doesn't have compression
> support (but qcow has the supported added)? For example, raw image
> backup with compression, "qemu-img convert -c -O raw origin.img
> dist.img", doesn't work.
A raw image is by definition a file that contains the exact same
sequence of bytes as the guest sees, without any additional information
or encoding. If you compress a raw file, the guest will see compressed
data on its hard disk instead of the real data.
Anything you could do to add transparent compression to it would mean
that it's not a raw image any more, but a new image format.
Kevin
next prev parent reply other threads:[~2020-10-20 8:02 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-20 1:31 Question on Compression for Raw Image Wang, Wei W
2020-10-20 8:00 ` Kevin Wolf [this message]
2020-10-20 14:22 ` Wang, Wei W
2020-10-20 14:32 ` Eric Blake
2020-10-20 14:42 ` Richard W.M. Jones
2020-10-20 14:49 ` Alberto Garcia
2020-10-20 14:36 ` Alberto Garcia
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20201020080051.GA4452@merkur.fritz.box \
--to=kwolf@redhat.com \
--cc=lersek@redhat.com \
--cc=mreitz@redhat.com \
--cc=qemu-block@nongnu.org \
--cc=qemu-devel@nongnu.org \
--cc=wei.w.wang@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).