"lio bod" <liobod.slony at gmail.com> writes:
> 2008/2/27, Christopher Browne <cbbrowne at ca.afilias.info>:
> Agree. It's always obvious once it's written.
>
>
>              - It is essential that a slon be kept running against the master
>           node, as if it is not, for a period of time, then when it
>           is restarted, that entire period of time will be treated as
>           One Big Long SYNC, and having such a huge SYNC is likely to
>           turn out badly :-(.
>
>
>  
>
> I don't catch the point
>
> The big sync may also turn badly if the slon 2 start and restart after a long time occures on the salve node.
>
> ?
>
> Thx anyway

No, the point is that if the slon for node #1 was running, throughout,
there won't be one single "very large SYNC."

If the slon for the master node *is* running, then there should be a
SYNC generated at least once every 2 minutes.  

Thus, if the slave DB is down for the weekend (e.g. -
Saturday/Sunday), then when you return on Monday, you'll find that the
slave node is behind by 2 days, and that the changes are divided up
across, um...  At least 1440 SYNCs (30 per hour, times 2x24).  If
there were times of heavy updates, there will more SYNCs than that.

In the catch-up process, the subscriber slon, on Monday, will be able
to gradually go through those changes, doing a COMMIT every so often,
so that the changes from the weekend will gradually flow in.

In contrast, if the slon for the "master" node was down for the
weekend, as well, then there will be just 1 SYNC, covering the time
from when the slon fell over until when it restarted.  There is no
ability to do the updates in more "bite-sized" pieces.
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