[libvirt] live migration copy-storage-all , inc

[Eric Blake]

On 05/17/2012 05:10 AM, Pankaj Rawat wrote:
> Hi all,
> I am currently doing live migration task KVM/qemu based virtual machine
> 
> I want to know what is exact difference between following:
> copy-storage-all option and copy-storage-inc option

copy-storage-all maps to qemu's 'blk' option, documented as:
block migration, full disk copy
[I think that means that qemu will copy the entire disk image onto the
destination]

copy-storage-inc maps to qemu's 'inc' option, documented as:
incremental disk copy
[I think that means that qemu will copy only the top file of a backing
chain, and assume that all other base files in the backing chain are
shared; but I could be wrong]

You might get better information from the qemu list on what these
options are supposed to do, and the difference between them.

> what are necessary steps for doing both?

Both options are relatively undertested at the moment, and patches are
welcome to help improve the matter.  In particular, copy-storage-all
currently has the lousy drawback that you, the user, must pre-create the
destination file with correct permissions and SELinux label (libvirt
_really_ should be doing this itself).

> 
> as per my knowledge 'copy-stoarage -all' migrates whole disk image to destination where 'copy-storage-inc' is when we use backing files for guest .
> with copy-storage-inc we require backing image on both destination and source but I want to know how destination guest get its base image how they share base image?
> Is there any link need to be created for this base image? or is there need for NFS ?
> 
> How to set up both options ? what are necessary steps need to follow before starting migration ?
> Please help me!

This is the sort of question that if anyone has ever successfully done a
non-shared migration (I personally have not tried it), then it would be
nice to document the steps they used on the wiki, as you are not the
first to ask about it.

> 
> The contents of this e-mail and any attachment(s) are confidential and

Unfortunately, you have posted to a publicly-archived list, where this
disclaimer cannot be enforced.  It is considered better netiquette to
post from a personal account rather than forcing us to read your
employer's legalese.

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

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