[infrastructures] state machines

[Willemse, Menno]

Hello World,

From: Wesley Craig <wes@umich.edu>
> On 20 Sep 2006, at 09:39, Brendan Strejcek wrote:
> > You have a deterministic backup (data and code that can reinstantiate
> > it) which behaves exactly as expected. However, between the time the
> > backup was taken and the time restored, some UID mappings were changed
> > on an external NIS or LDAP server, so files no longer have the correct
> > ownership.
> 
> This is a great example problem.  Thank you for a positive  
> contribution to the discussion.
> 
> If the backed up system had been running when the UID mapping  
> changed, how would that have been handled?

Maybe we should draw an analogy to database technology. An image backup (mksysb or some non-AIX equivalent) can be seen as a checkpoint in DB terminology. A restore will also include the machine state at the time it was run. Isn't it then simply a matter of rolling forward the actions between the time the backup was taken and Now? Of course, that does require that the change in ownership that accompanies the change in the LDAP server is also a logged action.

Without the occasional image backup, as far as I can tell, you are stuck replaying the whole history since time began. If you simply restore a backup, you won't have the latest changes. To get the whole thing, you need to do both.

Cheers,
Menno

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