[Asterisk-Users] MySQL replication for voicemail

[Damon Estep]

How many users are you supporting on a single 8 box using obdc/mysql
voicemail storage? Performance issues?

> -----Original Message-----
> From: asterisk-users-bounces at lists.digium.com [mailto:asterisk-users-
> bounces at lists.digium.com] On Behalf Of Josh McAllister
> Sent: Monday, May 08, 2006 2:06 PM
> To: Asterisk Users Mailing List - Non-Commercial Discussion
> Subject: RE: [Asterisk-Users] MySQL replication for voicemail
> 
> >
> > Hi Josh -
> >
> > > Another approach you may want to consider for data redundancy that
> > > does not rely on MySQL's finicky replication stuff is DRBD. Think
of
> it
> > > as RAID-1 across Ethernet. I have used it in production on some
VERY
> > > busy (> 1200 qps) MySQL servers for a couple years with no
problems.
> >
> > I would very much welcome not having to use a MySQL's replication
> > (sorry to all you MySQL geeks)!  I've read up a little on DRBD
before,
> > but I've avoided it in this particular application because of a few
> > questions I had about it:
> >
> > 1) Does it work over slow-ish links? In this case, I'm going over
WAN
> > links to offices around the country.
> 
> 
> This would be a function of the amount of data being changed, and the
> speed of your link. DRBD does support ASYNC mode, and there is a good
> chance this could work for you.
> 
> > 2) Can it do two-way replication?
> No. This is primarily because of the limitations of the overlying
> filesystem. (DRBD sits below the FS). With newer fs's like GFS, this
is
> now feasible, but DRBD is a little behind. Keep your eyes open for
0.8x
> to be released as it will support 2-way with GFS. If you want to
> maximize hardware resources, you can of course setup a partition
> replicating A -> B, and another replicating B -> A.
> 
> > 3) Can it do N-way replication (i.e. multiple slaves)?  We have
> > several offices offices that I'd like to have the replicated info.
> 
> 
> I know this was something that was in the works a while back. I
haven't
> followed this issue that closely though, so I'm not sure if this has
> been worked out or not. I believe the proposed approach was to simply
> get rid of some arbitrary limitations DRBD imposed on letting you
layer
> drbd on a drbd device.
> 
> >
> > Thanks!
> > Noah
> > _______________________________________________
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> 
> To summarize, if you are currently doing MySQL replication with
multiple
> masters, and multiple+N slaves, and you're trying to duplicate that...
> DRBD is probably not going to work for you. But I can say that what it
> does it does very well, and with little overhead. I've seen < 5%
> reduction in write performance with 15K SCSI drives, IE ~ 70MB/sec
> writes with DRBD vs ~72MB/sec without.
> 
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