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Old 03-29-2017, 01:57 PM   #1
fanoflq
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kvm : cloned image size is MUCH smaller!


I cloned a VM in KVM using this command:
Code:
# virt-clone --original centos7-1024ram-minimal \
           --auto-clone  \
	--name centos7-1024ram-minimal-clone0
And when I looked at resulting image size, it is MUCH MUCH smaller!
But it runs fine.
Code:
root@server /var/lib/libvirt/images # ls -alh
total 38G
drwx--x--x 2 root         root 4.0K Mar 28 12:55 .
drwxr-xr-x 7 root         root 4.0K Mar 28 16:15 ..
-rw------- 1 libvirt-qemu kvm  1.5G Mar 29 11:44 centos7-1024ram-minimal-clone0.qcow2
-rw------- 1 root         root 2.2G Mar 20 12:52 centos7-1024ram-minimal-clone.qcow2
-rw------- 1 root         root  15G Mar 14 10:07 centos7-1024ram-minimal.qcow2
Why is the image 10X smaller?
How to make its clone the same image size as original?

Thank you.

Last edited by fanoflq; 03-29-2017 at 02:40 PM.
 
Old 03-29-2017, 03:24 PM   #2
mddnix
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Registered: Mar 2013
Distribution: Redhat, Ubuntu
Posts: 526

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Quote:
Originally Posted by fanoflq View Post
I cloned a VM in KVM using this command:
Code:
# virt-clone --original centos7-1024ram-minimal \
           --auto-clone  \
	--name centos7-1024ram-minimal-clone0
And when I looked at resulting image size, it is MUCH MUCH smaller!
But it runs fine.
Code:
root@server /var/lib/libvirt/images # ls -alh
total 38G
drwx--x--x 2 root         root 4.0K Mar 28 12:55 .
drwxr-xr-x 7 root         root 4.0K Mar 28 16:15 ..
-rw------- 1 libvirt-qemu kvm  1.5G Mar 29 11:44 centos7-1024ram-minimal-clone0.qcow2
-rw------- 1 root         root 2.2G Mar 20 12:52 centos7-1024ram-minimal-clone.qcow2
-rw------- 1 root         root  15G Mar 14 10:07 centos7-1024ram-minimal.qcow2
Why is the image 10X smaller?
How to make its clone the same image size as original?

Thank you.
What's the output of this command?
Code:
virsh snapshot-list centos7-1024ram-minimal
 
Old 03-29-2017, 03:26 PM   #3
rknichols
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Quote:
Originally Posted by fanoflq View Post
Code:
# virt-clone --original centos7-1024ram-minimal \
           --auto-clone  \
	--name centos7-1024ram-minimal-clone0
And when I looked at resulting image size, it is MUCH MUCH smaller!
But it runs fine.
Code:
root@server /var/lib/libvirt/images # ls -alh
total 38G
drwx--x--x 2 root         root 4.0K Mar 28 12:55 .
drwxr-xr-x 7 root         root 4.0K Mar 28 16:15 ..
-rw------- 1 libvirt-qemu kvm  1.5G Mar 29 11:44 centos7-1024ram-minimal-clone0.qcow2
-rw------- 1 root         root 2.2G Mar 20 12:52 centos7-1024ram-minimal-clone.qcow2
-rw------- 1 root         root  15G Mar 14 10:07 centos7-1024ram-minimal.qcow2
My guess is that the original image was built with "Allocate entire disk now" checked for its 15GB image file. When the clone was made, only the space actually used was copied. If you run "qemu-img info" on that file, you'll see that its virtual size is 15GB, and it will grow up to that size as space is needed.
 
1 members found this post helpful.
Old 03-29-2017, 03:48 PM   #4
fanoflq
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Registered: Nov 2015
Posts: 397

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Quote:
Originally Posted by rknichols View Post
My guess is that the original image was built with "Allocate entire disk now" checked for its 15GB image file. When the clone was made, only the space actually used was copied. If you run "qemu-img info" on that file, you'll see that its virtual size is 15GB, and it will grow up to that size as space is needed.

Code:
# qemu-img info centos7-1024ram-minimal-clone0.qcow2
image: centos7-1024ram-minimal-clone0.qcow2
file format: qcow2
virtual size: 14G (15032385536 bytes)
disk size: 1.4G
cluster_size: 65536
Format specific information:
    compat: 1.1
    lazy refcounts: true
    refcount bits: 16
    corrupt: false
or this:
Quote:
# virsh domstats centos7-1024ram-minimal-clone0 | egrep -i "capacity|physical"
block.0.capacity=15032385536
block.0.physical=1528897536
Thanks.

Last edited by fanoflq; 03-29-2017 at 03:56 PM.
 
Old 03-29-2017, 03:50 PM   #5
fanoflq
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Registered: Nov 2015
Posts: 397

Original Poster
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Quote:
Originally Posted by mddnix View Post
What's the output of this command?
Code:
virsh snapshot-list centos7-1024ram-minimal

I got nothing!

Code:
# virsh snapshot-list centos7-1024ram-minimal
 Name                 Creation Time             State
------------------------------------------------------------

# virsh snapshot-list centos7-1024ram-minimal-clone0
 Name                 Creation Time             State
------------------------------------------------------------
#
 
Old 03-29-2017, 04:20 PM   #6
mddnix
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Registered: Mar 2013
Distribution: Redhat, Ubuntu
Posts: 526

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@fanoflq, rknichols is indicating at centos7-1024ram-minimal.qcow2 volume. You need to check for this volume. Check whether block.0.capacity and block.0.physical are same for centos7-1024ram-minimal.
 
Old 03-29-2017, 04:24 PM   #7
fanoflq
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Registered: Nov 2015
Posts: 397

Original Poster
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Quote:
Originally Posted by mddnix View Post
@fanoflq, rknichols is indicating at centos7-1024ram-minimal.qcow2 volume. You need to check for this volume. Check whether block.0.capacity and block.0.physical are same for centos7-1024ram-minimal.

Code:
# virsh domstats centos7-1024ram-minimal | egrep -i "capacity|physical"
  block.0.capacity=15032385536
  block.0.physical=15034941440
Same....almost
 
  


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