Andrew Sullivan wrote:
On Sun, Apr 05, 2009 at 11:36:33AM -0700, Lists wrote:
*Slony-I* - I've used this in the past, but it's a huge pain to work
with, caused serious performance issues under heavy load due to long
running transactions (may not be the case anymore, it's been a while
since I used it on a large database with many writes), and doesn't seem
very reliable (I've had replication break on me multiple times).
I'm also somewhat puzzled by the claim of unreliability:
most of the actual replication failures I've ever seen under Slony are
due to operator error (these are trivial to induce, alas --
aforementioned pain to work with again). Slony is baroque and
confusing, but it's specifically designed to fail in safe ways (which
is not true of some of the other systems: several of them have modes
in which it's possible to have systems out of sync with each other,
but with no way to detect as much. IMO, that's much worse, so we
designed Slony to fail noisily if it was going to fail at all).
From my experience - gained from unwittingly being in the wrong place
at the wrong time and so being volunteered into helping people with
Slony failures - it seems to be quite possible to have nodes out of sync
and not be entirely aware of it - in addition to there being numerous
ways to shoot yourself in the foot via operator error. Complexity seems
to be the major evil here.
I've briefly experimented with Londiste, and it is certainly much
simpler to administer. Currently it lacks a couple of features Slony has
(chained slaves and partial DDL support), but I'll be following its
development closely - because if these can be added - whilst keeping the
operator overhead (and the foot-gun) small, then this looks like a winner.
regards
Mark
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