[libvirt-users] virsh blockcopy: doesn't seem to flatten the chain by default

[Eric Blake]

On 07/02/2014 03:23 PM, Kashyap Chamarthy wrote:
> On Thu, Jul 03, 2014 at 12:42:20AM +0530, Kashyap Chamarthy wrote:
> 
> [. . .]
> 
> Forgot to note: Before blockcopy, the current block device is
> snap1.qcow2 (after too, it's the same, since we didn't `--pivot` to the
> copy.
> 

Not pivoting doesn't matter.  The point of a copy is that once the copy
is synced, you have two files that both get all new edits, and then you
break the sync leaving one file containing what the guest saw at that
point in time while the other file continues to track guest changes.
Aborting leaves the copy as the point in time, pivoting leaves the
original as the point in time.


>>
>> If I'm reading the man page of 'blockcopy' correctly, shouldn't it
>> 'flatten' the entire chain, by also copying the contents of base into
>> copy.qcow2? i.e. the 'copy' should have files (including the file foo
>> from 'base': 

A blockcopy only copies sectors of base into copy in the case where
those sectors were not already overwritten by sectors in snap1.

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

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