So having a Master-Master where you only write to one Master (lets say the
main one), you still need the increment and offset changed?
My guess is no, right?
From: Marcus Bointon [mailto:marcus@stripped]
Sent: quinta-feira, 27 de Outubro de 2011 10:55
To: Replication replication
Subject: Re: Master-Master -> duplicate entry
On 27 Oct 2011, at 09:51, Johan De Meersman wrote:
> Say what? If that's the case, you haven't set up your replication
correctly. There are quite a few reasons to not use both masters
concurrently, but this is not one of them.
Not at all. The point of redundancy (via replication or DRBD) is to maintain
consistent and available data in the face of a server or replication
failure. If you only write to one master at a time you have that. If you
write to both you have neither - i.e. it's actually worse than having no
redundancy at all, hence my statement. Because there is no performance gain
and there is an increased risk of data loss it's not just pointless, it's
actively bad. It's a bit like using RAID-0, but without the speedup! With
writes to both there's no way of avoiding the split-brain scenario you
describe and it's really hard to recover from (I've been there!). No
advantages plus lots of disadvantages sounds like a bad combo to me.
There are some attempts to introduce a semi-synchronous replication system
for MySQL that waits until transactions are replicated (possibly to a quorum
of slaves, much like Cassandra) before committing (or at least before
returning a result to the client).
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