[Spread-users] Re: [Wackamole-users] Query as to application of Wackamole and mySQL

[Theo Schlossnagle]

John David Duncan wrote:

>Here's how I do it:
>
>MySQL replication really does work, especially in the newer 3.23 releases.
>"Clustering" works via daisy-chained replication.
>
I would say MySQL replication "works as documented"... and you better 
read the documents before you assume someone else's definition of 
replication is the same as yours or mine.  IMNSHO MySQL doesn't 
replicate at all... Rather it does an excellent job of distributing 
transactions.

One quick example.  If I insert a row on machine A and machine B runs 
out of space when trying to apply that insert, it will not be inserted 
on B and will be on A and you have two accessible DBs without a 
consistent view.  The transaction never should have taken place unless 
it could be committed on all machines in the "replication pool".  MySQL 
provides nothing approaching this AFAIK.

MySQL allows applying ones transaction log to another database and 
cascading these into a daisy-chain -- where atomicity, consistency and 
integrity are maintained in all this is beyond me :-)

>If you don't have any tables with auto_increment keys, you can direct SQL
>inserts and updates to either server; otherwise it's best to direct all of
>the updates to a single host.
>  
>
My main point is that wackamole make no claims or efforts to provide 
application level replication.  It will never be the "mission" of 
wackamole.  Spread, on the other hand, is an excellent subsystem for 
building such a technology.  Spread could be used to implement ACID 
compliant replicated databases.

This discussion belongs on the MySQL or Spread lists (Spread-users IMHO 
so Ihave CCed it).

If you are in desperate need of such a replication technology, I would 
suggest talking to the guys are Spread Concepts, LLC.  Shoot Yair an email.

-- 
Theo Schlossnagle
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