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<div class="moz-cite-prefix">On 9/16/13 10:37 PM, Dolph Mathews
wrote:<br>
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<div class="gmail_quote">On Mon, Sep 16, 2013 at 5:31 AM,
Michael Still <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:mikal@stillhq.com" target="_blank">mikal@stillhq.com</a>></span>
wrote:<br>
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<div class="im">On Fri, Sep 13, 2013 at 7:51 AM, Dolph
Mathews <<a moz-do-not-send="true"
href="mailto:dolph.mathews@gmail.com">dolph.mathews@gmail.com</a>>
wrote:<br>
<br>
> ++ Data backups are a solved problem, and no DB
admin should trust an<br>
> application to perform its own backups.<br>
<br>
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I'm not completely sure I agree. Consider the case where a
cloud with<br>
active users undertakes an upgrade. The migrations run,
and they allow<br>
user traffic to hit the installation. They then discover
there is a<br>
serious problem and now need to rollback. However, they
can't just<br>
restore a database backup, because the database is no
longer in a<br>
consistent state compared with the hypervisors -- users
might have<br>
created or deleted instances for example.</blockquote>
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0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><br>
In this scenario if we could downgrade reliably, they
could force a<br>
downgrade with db sync, and then revert the packages they
had<br>
installed to the previous version.<br>
<br>
How would they handle this scenario with just database
backups?<br>
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<div>Great point, but I still wouldn't *rely* on an
application to manage it's own data backups :)</div>
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<br>
I don't think Michael was saying anybody should be relying on
migrations to manage its own backups but that it could serve an edge
case that database snapshots can not. In the scenario given I would
imagine that the administrators did have backups but wanted to avoid
using them to not lose any new data entered. If the migration
downgrade were to fail they would still have the backups and be no
worse off than they would have been without them. However if the
migration downgrade works then they get the benefit of not
(necessarily) losing new user data.<br>
<br>
Cheers,<br>
Josh<br>
<br>
--<br>
Rackspace Australia<br>
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class=""><font color="#888888"><br>
Michael<br>
<br>
--<br>
Rackspace Australia<br>
</font></span>
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-- <br>
<div><br>
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-Dolph
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