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From:Truls Bergskaug Date:May 21 2008 1:53pm
Subject:Re: replication architecture question
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On Wed, 2008-05-21 at 13:25 +0000, rwfrier@stripped wrote:
> 
>  So: 
> 1. if I've got a master on host 1 that's going to be replicated to a
> single mysql server on host 2. that server on host 2 can only contain
> slaves from 1 master, although it could contain n replicated db's from
> that 1 master (on host 1). correct?
A single host can have more than one instance of MySQL-server running
(See  http://dev.mysql.com/doc/refman/5.0/en/mysqld-multi.html ). Each
instance can have several databases.

> 2. With that configuration, a query could be run on server 2 that
> joins data from it's 'local' databases and the replicated db from
> server 1. correct?
Yes

> 3. If I then had server 3 that contains other databases, I'd have to
> set it up as a slave to server 2, so that replication of server 1
> would 'pass through' to server 3, and databases from server 2 would
> then be replicated to server 3, thereby allowing queries that would
> join data from server 1, server 2, and server 3. correct?
This is one way to do it or use federated tables
http://dev.mysql.com/doc/refman/5.0/en/federated-storage-engine.html
could be a solution.

> 4. Does this mean that db's from server 1 are replicated twice? on
> server 2 and then server 3?
Yes
> 5. Does this mean that db's from server 2 are replicated only once, to
> server 3?
Yes

You could also have two instances on host 2 that (one is slave for host
1 and the other for host 3) and use federated tables to link them
together.

Truls Bergskaug

> 
> Thanks again.
> -Russ
> 
> 
> 
>         -------------- Original message from "ewen fortune"
>         <ewen.fortune@stripped>: -------------- 
>         
>         
>         > Hi Russ, 
>         > 
>         > On Tue, May 20, 2008 at 10:33 PM, wrote: 
>         > > need to make sure that I'm understanding this correctly: 
>         > > 1. a single mysqld_safe can either be a MASTER or SLAVE,
>         such that all of 
>         > > it's database are either masters or slaves - can't have a
>         mix of slaves and 
>         > > masters under the same mysqld_safe. Is this correct? 
>         > 
>         > mysqld_safe is just script that sets up logging and starts
>         the mysqld instance 
>         > 
>         > Each instance can be either master, slave or both if you
>         wanted to 
>         > setup some sort of a tree hierarchy 
>         > A master can have multiple slaves, but a slave can have only
>         one master 
>         > 
>         > > 2. Queries involving more than 1 database - can a single
>         query pull data 
>         > > from databases served by different mysqld_safe's, even if
>         they're on the 
>         > > same physical host? 
>         > 
>         > You can do this using federated tables 
>         >
>         http://dev.mysql.com/doc/refman/5.0/en/federated-storage-engine.html 
>         > 
>         > > 
>         > > In other words - I need to have a single query that
>         combines data from a 
>         > > slave database and a stand-alone (non-replicated mysql
>         database). Doable? 
>         > > I appreciate your effort in helping me with this. 
>         > 
>         > Take a look at the federated table stuff, it would allow you
>         to query 
>         > tables from other MySQL instances. 
>         > 
>         > Ewen 
>         > 
>         > > -Russ 
>         > > 
>         > > 
>         > 
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Thread
replication architecture questionrwfrier20 May
  • Re: replication architecture questionewen fortune20 May
    • Re: replication architecture questionrwfrier21 May
      • Re: replication architecture questionTruls Bergskaug21 May