Incidentally, this is something that is being focussed on as part of
the upcoming release [1]. 

[1] https://cwiki.apache.org/confluence/x/v5YTAg

On Tue, Nov 05, 2013 at 10:42:58PM +0000, Marty Sweet wrote:
> The issue with plain MySQL replication (espically in master-master) is that
> a failed query will stop replication. A good example of this is when an
> record is added onto each master at the same time (within a second), say a
> new record which gets the same primary key and replication will stop, on
> both hosts. That then leaves a split brain situation when you have one
> master writing its own data and another writing to itself, all with
> identical primary keys. Absolute nightmare. This can how ever be migrated
> with the methods the OP mentioned (I assume - but don't have experience of).
> 
> I don't think file curroption is much of an issue with DRDB, but you can
> only have one host write to it at anyone time (limitation of file system
> used), which makes the master-slave or master-backup setup ideal when
> coupled with HA service management software such as Pacemaker. You then
> have the database files in both places without the dreaded MySQL
> replication stories.
> 
> I think the main question lyes with if the cloud admin wants a
> simple redundant setup or a load balanced service - it may also we worth
> writing some documentation for this to help future installations, although
> they will have to be detailed.
> 
> I have never used Percona/MariaDB, does it resolve the master-master issues
> I mentioned earlier?
> 
> Marty
> 
> On Tuesday, November 5, 2013, Adrian Lewis wrote:
> 
> > Seems like the Percona solution also uses Galera for their multi-master
> > cluster. Starting to wonder whether to go MariaDB-Galera now. Tempted just
> > to leave it as master slave replicated on MySQL though. Scale really not
> > an issue right now. Ho hum, fun to be had if I had the time to play.
> >
> > Assuming no Galera (with either MySQL/Percona/MariaDB) and just using
> > Centos version of MySQL - does anyone have any input as to whether to go
> > for replicating between two hosts using DRBD vs native MySQL replication?
> > I get the impression that MySQL replication is an eventually-consistent
> > near-realtime kind of replication whereas DRBD can be set to be completely
> > synchronous replication. MySQL replication just seems a lot less fiddly
> > than using DRBD and DRBD would replicate file corruption that MySQL
> > replication would be largely safe from.
> >
> > -----Original Message-----
> > From: Patrick Miller [mailto:patrick.mil...@sungard.com <javascript:;>]
> > Sent: 05 November 2013 21:51
> > To: users@cloudstack.apache.org <javascript:;>
> > Subject: Re: Multi-master MySQL Setup
> >
> > Take a look at the percona [1] implementation of mysql and there clustered
> > version.
> > Round robin reads and writes supported.
> >
> > 1] http://www.percona.com/
> >
> >  Patrick
> >
> >
> > On Tue, Nov 5, 2013 at 9:55 AM, Adrian Lewis
> > <adr...@alsiconsulting.co.uk <javascript:;>>wrote:
> >
> > > Hi Marty/Nux!,
> > >
> > > Thanks for the feedback - sounds like multi-master is not a good thing
> > > then! Load will likely be very small for at least the next 6 months
> > > but I figured that it was one of those things that could be set easily
> > > now (still setting up) that I might appreciate later.
> > >
> > > Based on both your responses, I think I'll just leave it well alone!
> > > Need to get to grips with pacemaker/corosync anyway for other reasons
> > > so I'll just try that with either DRBD replication or MySQL replication.
> > >
> > > Cheers,
> > >
> > > Adrian
> > >
> > > -----Original Message-----
> > > From: Marty Sweet [mailto:msweet....@gmail.com <javascript:;>]
> > > Sent: 05 November 2013 17:23
> > > To: users@cloudstack.apache.org <javascript:;>
> > > Subject: Re: Multi-master MySQL Setup
> > >
> > > Others may have had more success with this but from experience of
> > > MySQL in multi-master setups I would avoid this entirely.
> > >
> > > A common setup is using DRDB to provide a master/slave:
> > > Management 1 (MySQL Master) w/ virtual IP Management 2 (MySQL Slave)
> > >
> > > HA IP Address (for agents/services requiring DB write) which is
> > > assigned to the master (using Pacemaker).
> > >
> > > You can then send web management client to the HA IP Address as well.
> > >
> > > It may be worth considering if you need load balancing, depending on
> > > your setup - what loads are you experiencing?
> > >
> > > Marty
> > >
> > >
> > >
> > > On Tue, Nov 5, 2013 at 5:13 PM, Adrian Lewis
> > > <adr...@alsiconsulting.co.uk <javascript:;>>wrote:
> > >
> > > > Hi All,
> > > >
> > > >
> > > >
> > > > Just wondering if anyone is using a MySQL multi-master configuration
> > > > with auto_increment_offset (e.g.10) and auto_increment_increment (1
> > > > for server 1, 2 for server 2 etc)? Does it work? Does anyone know a
> > > > reason why it doesn't or wouldn't work? Is there anything from an
> > > > application point of view that could/would trip up CS if
> > > > auto_increment values are set as more than 1?
> > > >
> > > >
> > > >
> > > > Not planning on deploying multimaster just yet but if I at least
> > > > start with an auto_increment of 10, I'd have the option of adding a
> > > > second master later and being able to load-balance more effectively.
> > > >
> > > >
> > > >
> > > > Thanks in advance,
> > > >
> > > >
> > > >
> > > > Adrian
> > > >
> > >
> > >
> >

-- 
Prasanna.,

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