libvirt users - Apr 2012 - vol-wipe and delete

Hello all,

 

I know libvirt has the following two commands:

 

vol-wipe

 

vol-delete

 

Can someone please explain to me how these function?  Do these only remove
previous session data so that a new virtual instance cannot see it or does
it remove it at the physical level level too so that the data cannot be
found anywhere on the physical drive?  I know Eucalyptus and KVM use sparse
files upon instance creation and the instance thinks the ephemeral space is
all zeroes even though it is just sparse.   I appreciate any insight in how
the two virsh commands work and if they use zeroes, sparse, or some other
method.

 

Thanks,

Shawn

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On 04/10/2012 06:20 PM, Shawn Davis wrote:
> Hello all,
> 
>  
> 
> I know libvirt has the following two commands:
> 
>  
> 
> vol-wipe
calls virStorageVolWipe or virStorageVolWipePattern (depending on
arguments), which overwrites the existing data with all 0 or with a
specific pattern.  The file stays intact, but future uses of the file
will no longer see the data that had been there previously.
> 
>  
> 
> vol-delete
calls virStorageVolDelete, which removes the file but does not wipe it
(so the data is still present on the backing storage device).
> 
>  
> 
> Can someone please explain to me how these function?  Do these only remove
> previous session data so that a new virtual instance cannot see it or does
> it remove it at the physical level level too so that the data cannot be
> found anywhere on the physical drive?
If you want the data removed at the physical layer, use vol-wipe.

-- 
Eric Blake   eblake at redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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