Master Master Replication ... do a fail over and a week agos data is revealed.

[short cutter]

Hiya
I run MySQL Master - Master Replication. Ive had an interesting situation
whereby I failed over using heartbeat but whats is interesting  is that via
the application (vbulletin), I see that the forums was showing that a weeks
ago data.

Why using M-M replication?
The book of "High performance Mysql" says it is not a reliable mechanism.

Regards.

[Walter Heck - OlinData.com]

To Clarify this a bit: You can only reliably do writes to one server.
Your reads can go to both servers with no problems.
For reads that need to read data that was just written though, you
need to read from the 'active' master, as you can not rely on
replication to be instantaneous.

Johan,
You state that master - master is not reliable in dual active environments.
I am in the process of setting up just such an environment (moderate active
on the primary server, lighter activity on the other server.)  Do you know
where I can get some information on the risks?

On the MySQL site, I guess :-) Your major issue is likely to be the lack of
even if you properly interleave your autoincrements, the lack of a true
global lock means you still risk conflicting updates.
I can't really tell you a single spot where I got my knowledge on the
subject - I'm a long-time and multi-platform DBA, so it's a combination of
stuff I read and an understanding of how things work - or don't.
--
Bier met grenadyn
Is als mosterd by den wyn
Sy die't drinkt, is eene kwezel
Hy die't drinkt, is ras een ezel

[Johan De Meersman]

On Wed, Oct 20, 2010 at 1:37 AM, Walter Heck - OlinData.com <

Post by Walter Heck - OlinData.com
To Clarify this a bit: You can only reliably do writes to one server.

Also not *entirely* true: nothing prevents you from using the two masters
for distinct databases - or even tables - and just having them as mutual
hot-standby.

It's very important to realise that replication does NOT scale your write
capabilities, though: every write that happens on one side must also happen
on the other side.