Re: [Xen-users] Hot Copy file based VMs

[Jan Kalcic <jandot@xxxxxxxxxxxxxx>]

Javier Guerra wrote:
> On Wed, Mar 18, 2009 at 10:46 AM, Jan Kalcic <jandot@xxxxxxxxxxxxxx> wrote:
>   
> > What do you mean with "atomic" copy?
> >
> >     
> when talking about storage (or data access in general), an operation
> is 'atomic' from some point of view if it's 'indivisible'. that is,
> there wasn't any point in time when it was 'halfway done'.
>
> LVM snapshots manage this, because it's not a real copy (it's more
> like a fork, but it works like a copy in most cases), and because it
> taps the main stream of storage operations.
>
> most other kinds of copy can't be really atomic, that's why Fajar
> tells you to suspend the guest while you do the copy.  that way, even
> if there was a time when the copy was half-done, the guest wasn't
> really there, so from it's point of view, the copy was atomic.
>
>   
I see. Really  thanks,
Jan

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