2:52 a.m.
On Wed, Jun 22, 2016 at 05:56:09PM -0500, libvirt_users(a)skagitattic.com wrote:
> Delete what you've done and start from the beginning.
Describe
> exactly how you created the guest. Use 'qemu-img info' to show the
> format of the input file. Show precisely the virt-sparsify command
> you are running. And use 'qemu-img info' on the output file too.
Okay, here goes. Start off with an install
root@testingbox:~ # virt-install --name testimage --memory 512 -l
'http://ftp.nl.debian.org/debian/dists/jessie/main/installer-amd64/'
--disk size=50 --nographics -x "console=ttyS0"
Starting install...
Retrieving file
MANIFEST...
| 3.3 kB 00:00 ... Retrieving file
linux...
| 6.0 MB 00:03 ... Retrieving file
initrd.gz...
| 29 MB 00:09 ... Allocating
'testimage.qcow2'
| 50 GB 00:00 Creating
domain...
| 0 B 00:00 Connected to domain testimage Escape character is
[ 0.000000] Initializing cgroup subsys cpuset [ 0.000000]
Initializing cgroup subsys cpu [ 0.000000] Initializing cgroup
subsys cpuacct [ 0.000000] Linux version 3.16.0-4-amd64
(debian-kernel(a)lists.debian.org) (gcc version 4.8.4 (Debian 4.8.4-1)
) #1 SMP Debian 3.16.7-ckt25-2 (2016-04-08)
.... Many more lines here and it turns interactive. Suffice it to
say I did a basic minimal install following the prompts. Nothing
special here.
This created an image that is 2.5G with a 50G apparent size and
identifies as qcow2 as shown below.
# ls -slh testimage.qcow2
2.5G -rw-r--r-- 1 root root 51G Jun 22 20:22 testimage.qcow2
# qemu-img info testimage.qcow2
image: testimage.qcow2
file format: qcow2
virtual size: 50G (53687091200 bytes)
disk size: 2.4G
cluster_size: 65536
Format specific information:
compat: 1.1
lazy refcounts: true
Now we sparsify (/bigtmp is on a larger partition then / to give
virt-sparsify enough room to work with so it does not complain).
root@testingbox: 08:59 PM # virt-sparsify testimage.qcow2
testimage1.qcow2 --tmp /bigtmp Input disk virtual size = 53687091200
bytes (50.0G) Create overlay file in /bigtmp to protect source
disk ... Examine source disk ...
100%
⟦▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒⟧
--:-- Fill free space in /dev/sda1 with zero ... 100%
⟦▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒⟧
00:00 Clearing Linux swap on /dev/sda5 ... 100%
⟦▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒⟧
--:-- Copy to destination and make sparse ...
Sparsify operation completed with no errors. Before deleting the
old disk, carefully check that the target disk boots and works
correctly.
root@testingbox: 09:04 PM #
This image reports still reports as qcow2 however the apparent and real
size is the same.
# ls -slh testimage1.qcow2
1.1G -rw-r--r-- 1 root root 1.1G Jun 22 21:04 testimage1.qcow2
# qemu-img info testimage1.qcow2
image: testimage1.qcow2
file format: qcow2
virtual size: 50G (53687091200 bytes)
disk size: 1.1G
cluster_size: 65536
Format specific information:
compat: 1.1
lazy refcounts: false
virt-sparsify saved about 1.3 GB of disk space (2.4G -> 1.1G).
If we try it again but specify raw its MUCH faster
root@testingbox: 09:26 PM # virt-sparsify testimage.qcow2
testimage2.qcow2 --tmp /bigtmp --format raw
This is incorrect usage. You've told virt-sparsify that the input
image is raw. But it's not raw, it's qcow2.
In any case, virt-sparsify opened the image as raw, couldn't make any
sense of it (it appears to virt-sparsify to be random data, not a disk
image), and so it cannot sparsify it properly. This is "quicker" only
because virt-sparsify didn't do any sparsification of filesystems,
because it couldn't see the filesystems.
This time it takes up more space and reports real and apparent size
differently. It still reports as qcow2 with qemu-img.
# ls -slh testimage2.qcow2
1.7G -rw-r--r-- 1 root root 51G Jun 22 21:27 testimage2.qcow2
# qemu-img info testimage2.qcow2
image: testimage2.qcow2
file format: qcow2
virtual size: 50G (53687091200 bytes)
disk size: 1.7G
Looks like virt-sparsify still found some clusters containing all
zeroes which it could trim, even though it didn't know how to read the
disk.
Anyway, the moral is, don't misinform virt-sparsify of the format
of your input image.
If what you really intended to do was to convert the format from qcow2
to raw, you should use '--convert raw' instead.
The only things I see different from the finished files is that the
raw
one uses a bit more space, the apparent size is not set to the
virtual size on the default sparsify one and the lazy refcounts is
different.
Is there something more detailed then "qemu-img info" that I could tell
the difference with?
qemu-img info is the correct tool to use.
> Raw has fewer features, especially no simple snapshotting or
support
> for backing files.
I wrote this thinking you were talking about actual raw format disks,
not about qcow2 but where you've misinformed virt-sparsify about the
format.
Is simple snapshotting using qemu-img snapshot or something else? I
tried making a snapshot with both test images and they both appeared to
work.
http://wiki.qemu.org/Documentation/CreateSnapshot
# qemu-img snapshot -c test testimage1.qcow2
# qemu-img snapshot -c test testimage2.qcow2
# qemu-img info testimage2.qcow2
image: testimage2.qcow2
file format: qcow2
virtual size: 50G (53687091200 bytes)
disk size: 1.7G
cluster_size: 65536
Snapshot list:
ID TAG VM SIZE DATE VM
CLOCK 1 test 0 2016-06-22 22:41:52
00:00:00.000 Format specific information:
compat: 1.1
lazy refcounts: true
This works because testimage2.qcow2 is still in qcow2 format.
Anyway, use the correct --format option.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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