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[virt-tools-list] Sparse in Virt-clone



 

Hi all,

 

I am trying to clone a lvm2 image following thing haapens when I clone a image with virt-clone command

 

virt-clone --prompt --force --original  lvm_thin_1 --name  lvm_thin_2 --file /dev/volgrp/lvm_thin2

 

Now when I clone this,  It clone successfully but the cloned image is fully expanded ,  I mean it takes all 100% space

 

#lvs

 

LV

VG

Attr

LSize

Pool Origin

Data%

lvm_thin_1

Volgrp

Vwi-aotz

8.00g

pool

10.18

lvm_thin_2

volgrp

Vwi-a-tz

8.00g

pool

100.00

pool

volgrp

twi-a-tz

100.00g

 

8.97

                                                                                                                           

 

Now as you can see The 2nd lvm thin disk is fully expanded to 100%

 

I then downloaded the virtinst source code from the http://virt-manager.org/ site

Package:-  virtinst-0.600.3.tar.gz

 

The I dig into to the code

 

Now  here is what I notice

In file VirtualDisk.py

Function:-    def  _clone_local(self, meter, size_bytes)

 

I changed some code

Here is the diff

 

[root localhost work]# diff changedcode/virtinst-0.600.3/virtinst/VirtualDisk.py virtinst-0.600.3/virtinst/VirtualDisk.py

1383a1384

>         clone_block_size = 4096

1391a1393

> 

1399c1401

<                     if sparse and zeros == l:

---

>                     if  zeros == l:

1411a1414

> 

 

 

Here I removed the sparse from the condition, and also change the cloned_block_size(varying this value change the cloned image size to some extent)

Initially the sparse is false That’s why the condition is not checked , I skipped that part

 

Now

#lvs

 

LV

VG

Attr

LSize

Pool Origin

Data%

lvm_thin_1

Volgrp

Vwi-aotz

8.00g

pool

10.18

lvm_thin_2

volgrp

Vwi-a-tz

8.00g

pool

8.51

pool

volgrp

twi-a-tz

100.00g

 

8.97

                                                                                                                           

As you can see clone disk is even more compressed, as all the unnecessary zeros are removed from the source file.

The cloned VM is working file , I double checked it.

 

Now I am not sure whether this is a correct solution for cloning,

 

What I actually want to know is what actually sparse is representing here, why it was initially set to false?

And it what case the sparse condition is actually met?

 

Regards

Pankaj Rawat

 


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