Backups?

[Chris Muller]

Hi Göran, the fault tolerance was designed from the ground up to handle
a sudden power outage.  Specifically, under the assumption that writes
to the various db files could be partially completed to any point in
time, but a common point in time between all files.

This is a different situation than copying on-line files because the
copy could take some time, even spanning multiple flushes (which are,
by default, every 5 seconds).  The former is a much easier scenario to
consider because, in the latter, the partially-written state of each
file is from a different time than all the other files.

I certainly would not risk it.  You should close the DB files before
doing a backup.

I have sketched out a plan for replication where on-line backup is a
nice side-effect.  But that might be a while so, until then, I would
definitely bring down the DB to do a backup.

 - Chris


--- goran at krampe.se wrote:

> Hi Chris and all!
> 
> Ok, we are getting closer to first test deployment of our app for a
> few
> user groups and (since we may experience problems, like db corruption
> (heaven forbid) or simply bugs in the app causing havoc) I want to
> make
> extra sure that I have a good approach regarding backups.
> 
> Am I correct that since we now have fault tolerance I could
> essentially
> just copy the db files to get a backup of the db - even though it
> will
> not be transactionally correct? I mean - I can lose the ongoing txns,
> but the copy should otherwise be able to recover and work, right?
> 
> Or do I need to make a shutdown in order to make sure I get a
> "proper"
> backup?
> 
> regards, Göran
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