Comments on: How expensive is MySQL Replication for the Master

By: Bay

Bay — Fri, 18 Mar 2011 15:18:15 +0000

correct me if I am wrong, blackhole engine has its limitations, only has insert trigger, no update and delete trigger, can not support auto-increment keys, it is not reliable and often break replications.

By: Diego Cassinera

Diego Cassinera — Tue, 18 Jan 2011 14:20:58 +0000

Good idea regarding the interrupts, however, if you are talking about the cost of slaves you did not get into memory usage. In order for the server to deal with the different lag of each slave, it need to have a stream of operations for each slave. In most cases most of the slaves are on the same binlog, but when they are not multiple binlogs will be in memory,

On large systems, it makes total sense to stream a binlog to one system, and this system propagates to the rest.
Using black hole you could do this in a pyramid fashion.

By: Mark Callaghan

Mark Callaghan — Wed, 20 Jan 2010 06:50:33 +0000

I think I want the blackhole slave to run on the same server as the master. That will eliminate the cost of extra hardware and networking. The cost of managing the extra servers still exists. I think the rise of the cloud and MySQL running on it will spur the development of frameworks that make it easier to manage large numbers of mysql instances. I don’t think we have good frameworks yet that make it easy to manage the extra servers.

By: zerkms

zerkms — Wed, 20 Jan 2010 02:09:04 +0000

@Mark
nice pov but money isn’t the absolute measure for “cost”. due to facebook practice, let imagine 1 (one) master server which serve 4 datacenters. what will be it’s bandwidth?

ps: like your posts at MySQL@Facebook

By: Mark Callaghan

Mark Callaghan — Wed, 20 Jan 2010 01:47:31 +0000

@zerkms – there is a cost from buying and managing the extra server. I don’t want to manage another server.

By: zerkms

zerkms — Tue, 19 Jan 2010 00:18:22 +0000

yeah, but the discussion is around topic sounds like “How expensive is MySQL Replication for the Master”
and in this case it costs in only one slave at all

By: peter

peter — Mon, 18 Jan 2010 16:40:16 +0000

Yes. It will be moved to the different box but not going away

By: zerkms

zerkms — Mon, 18 Jan 2010 05:43:08 +0000

hmmm…… why overhead not going avay?
it will be removed to dedicated “blank”-blackholed server and the master now will have to serve just 1 slave, instead of N.

By: peter

peter — Mon, 18 Jan 2010 05:39:32 +0000

zerkms,

You can use blackhole to build the tiered replication of course but it is complication and the overhead is not going away in this case – you will still need to spend a lot of CPU cycles if you’re feeding many slaves with current architecture they can just be split against several intermediatery slaves.

By: peter

peter — Mon, 18 Jan 2010 05:37:59 +0000

Robert,

My idea is about replication is simple – any traffic Master server is able to handle it should be able to replicate onto the slave if it is the same configuration. I also would like to see replication not taking too much overhead on the master. Currently you can get about 50.000 simple transactions a second (something like update by primary key) so this is the number.