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From Prasanna Santhanam <...@apache.org>
Subject Re: Multi-master MySQL Setup
Date Wed, 06 Nov 2013 10:34:50 GMT
Hi Alex,

The wiki is a WIP for the feature that is on the roadmap. This
discussion should serve well when drawing out the specifics of
database-ha. Please do not hesitate to weigh in when you see the
[DISCUSS] thread related to 'Database-HA' on the dev@ mailing list.

On Wed, Nov 06, 2013 at 03:10:02PM +0800, Alexey Zilber wrote:
> Hi Prasanna,
> 
>   That page isn't fully correct regarding MariaDB.  Please see:
> https://mariadb.com/kb/en/multi-source-replication/
> 
> Thanks,
> Alex
> 
> 
> On Wed, Nov 6, 2013 at 2:35 PM, Prasanna Santhanam <tsp@apache.org> wrote:
> 
> > 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.miller@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
> > > > <adrian@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.dev@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
> > > > > <adrian@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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> >
> >

-- 
Prasanna.,

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