[fedora-virt] porting a disk from lvm to file

[Richard W.M. Jones]

On Sun, Aug 22, 2010 at 10:31:55PM +0300, Avi Kivity wrote:
>  On 08/22/2010 10:02 PM, Richard W.M. Jones wrote:
> >>Interesting, I'd have guessed that encryption will dominate the cpu
> >>cost, and that compression would be a win since there's less to
> >>encrypt and transmit.
> >Maybe my explanation is wrong too.  virt-p2v was definitely much
> >slower when we added the '-C' option.  However read on.
> >
> >I just ran a test again on my local LAN.  This is between two
> >approximately equal Fedora machines, over a moderate quality consumer
> >gigabit ethernet switch.  The command approximates what virt-p2v does:
> >sending 1MB blocks from local /dev device, and at the target end using
> >cat to write to a file.
> >
> >$ time sh -c 'dd bs=1M if=/dev/vg_trick/Windows7x64 | ssh amd "cat>  /tmp/copy1"'
> >16384+0 records in
> >16384+0 records out
> >17179869184 bytes (17 GB) copied, 1473.26 s, 11.7 MB/s
> >
> >real	    24m33.269s
> >user	    4m16.944s
> >sys	    4m43.181s
> 
> 11.7 MB/s = 93.6 Mb/s.  Not the cpu is not loaded.  Are you sure
> you're using 1GbE here?

You're absolutely right -- I forget that it's a fast ethernet switch :-)

> >$ time sh -c 'dd bs=1M if=/dev/vg_trick/Windows7x64 | ssh -C amd "cat>  /tmp/copy2"'
> >16384+0 records in
> >16384+0 records out
> >17179869184 bytes (17 GB) copied, 1412.7 s, 12.2 MB/s
> >
> >real	    23m32.736s
> >user	    17m52.739s
> >sys	    5m0.884s
> >
> 
> Suddenly you're cpu bound.  So it looks like compression is really
> expensive for some reason.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
New in Fedora 11: Fedora Windows cross-compiler. Compile Windows
programs, test, and build Windows installers. Over 70 libraries supprt'd
http://fedoraproject.org/wiki/MinGW http://www.annexia.org/fedora_mingw