From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35524) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XHHgC-0006gz-R5 for qemu-devel@nongnu.org; Tue, 12 Aug 2014 15:24:22 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XHHgB-0000Ey-Bn for qemu-devel@nongnu.org; Tue, 12 Aug 2014 15:24:20 -0400 Received: from mail-ig0-x22e.google.com ([2607:f8b0:4001:c05::22e]:61468) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XHHgB-0000Es-52 for qemu-devel@nongnu.org; Tue, 12 Aug 2014 15:24:19 -0400 Received: by mail-ig0-f174.google.com with SMTP id c1so7856987igq.13 for ; Tue, 12 Aug 2014 12:24:18 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20140812185207.GH14001@redhat.com> References: <20140812184630.GP8471@redhat.com> <20140812185207.GH14001@redhat.com> From: Xingbo Wu Date: Tue, 12 Aug 2014 15:23:38 -0400 Message-ID: Content-Type: multipart/alternative; boundary=047d7bd752e42b56600500739eae Subject: Re: [Qemu-devel] disk image: self-organized format or raw file List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Richard W.M. Jones" Cc: qemu-devel@nongnu.org --047d7bd752e42b56600500739eae Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Tue, Aug 12, 2014 at 2:52 PM, Richard W.M. Jones wrote: > On Tue, Aug 12, 2014 at 07:46:30PM +0100, Daniel P. Berrange wrote: > > Taking the compression feature - arguably the biggest benefit of that > > is when you distribute disk images. eg if someone provides a root disk > > image on a web server, using compression in qcow2 can dramatically > > lower the download size, while still allowing QEMU to directly run > > from that qcow2 file. Sure you could wrap your disk images in gzip > > and then convert to your local filesystem at time of use but this > > introduces multiple extra steps. > > It would be nice if qemu could handle xz-compressed files > transparently, since (when prepared correctly) these files are > seekable. > > I have written code to do this here: > > https://github.com/libguestfs/nbdkit/tree/master/plugins/xz > > I believe it's ideal for read-only backing file, the xz-compressed image would be very space efficient for distribution :). Would you consider replace xz with lz4? it has faster decompression speed (~500MB/s)[1] and client-side decompression would be made painless. [1] http://linuxaria.com/article/linux-compressors-comparison-on-centos-6-5-x86= -64-lzo-vs-lz4-vs-gzip-vs-bzip2-vs-lzma > Rich. > > -- > Richard Jones, Virtualization Group, Red Hat > http://people.redhat.com/~rjones > Read my programming and virtualization blog: http://rwmj.wordpress.com > libguestfs lets you edit virtual machines. Supports shell scripting, > bindings from many languages. http://libguestfs.org > --=20 Cheers! =E5=90=B4=E5=85=B4=E5=8D=9A Wu, Xingbo --047d7bd752e42b56600500739eae Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable



On Tue, Aug 12, 2014 at 2:52 PM, Richard W.M. Jones <rjones@redhat= .com> wrote:
On Tue, Aug 12, 2014 at 07:46:30PM +0100, = Daniel P. Berrange wrote:
> Taking the compression feature - arguably the biggest benefit of that<= br> > is when you distribute disk images. eg if someone provides a root disk=
> image on a web server, using compression in qcow2 can dramatically
> lower the download size, while still allowing QEMU to directly run
> from that qcow2 file. Sure you could wrap your disk images in gzip
> and then convert to your local filesystem at time of use but this
> introduces multiple extra steps.

It would be nice if qemu could handle xz-compressed files
transparently, since (when prepared correctly) these files are
seekable.

I have written code to do this here:

=C2=A0 https://github.com/libguestfs/nbdkit/tree/master/plug= ins/xz

I believe it's ideal for re= ad-only backing file, the xz-compressed image would be very space efficient= for distribution :).
Would you consider replace xz with lz4? it = has faster decompression speed (~500MB/s)[1] and client-side decompression = would be made painless.

Rich.

--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
libguestfs lets you edit virtual machines. =C2=A0Supports shell scrip= ting,
bindings from many languages. =C2=A0http://libguestfs.org



--

Cheers!
=C2=A0 =C2=A0 =C2=A0 =C2=A0=E5=90=B4=E5=85=B4=E5=8D=9A = =C2=A0Wu, Xingbo <= wuxb45@gmail.com>
--047d7bd752e42b56600500739eae--