[Fedora-infrastructure-list] Database for Account System 2

[Jonathan Steffan]

Curt Moore wrote:
>> There are two good projects, slony-i_ and pg-cluster, that support
>> master-slave replication and multi-master replication respectively.  I
>> haven't used either but Curt Moore mentioned he uses slony-i during one
>> of the IRC meetings.
>>     
>
> Yes, I use Slony-I in my production environment and like most other
> complex software packages, it works quite well if it's configured
> correctly.  As Toshio mentioned, Slony-I is a single master, multi-slave
> architecture so write operations can only be performed to a master DB
> and those changes then have to be replicated down to the slave servers.
> There are provisions for promoting a slave to be the master server in
> case the master crashes but they advise doing everything humanly
> possible to ensure that this doesn't happen.
>
>   
>> slony-i_ http://gborg.postgresql.org/project/slony1/projdisplay.php
>> pg-cluster_ http://pgfoundry.org/projects/pgcluster/
>>
>>     
>
> The last time I experimented with PGCluster, which is
> multi-master/multi-slave, probably around Oct/Nov of 2005, I was using
> PostgreSQL 8.0.1 and it wasn't that well supported at that time.  Its
> architecture was also quite hardware intensive in order to avoid a SPOF,
> which wouldn't have been a big deal to me if it had worked.  The project
> has since progressed and I believe they have improved support for
> Postgres 8.x so it may warrant further investigation in our discussions
> for DB replication; I've just not had time to get around to testing the
> updated versions in my environment.
>
> -Curt
>
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>   

Replication is very attractive when setting up authentication systems. I
ask because of the following:

--snip--

Fedora Directory Server uses the Berkley Database as it's data store.
This data store is very high performance and is transacted to ensure
ACID data updates. Fedora DS automatically detects if the data was not
written cleanly and does a database restore at startup if necessary.
Multiple databases provide a simple way of breaking down your directory
data to simplify the implementation of replication and chaining in your
directory service. Import into one suffix without affecting the other
suffixes.

FDS supports 4-Way Multi-master replication. Multi-master means the
ability to write to two or more masters at the same time, with automatic
conflict resolution, as opposed to just having one master at a time with
hot failover. This feature provides a highly available directory service
for both read and write operations. Multi-master replication can be
combined with simple and cascading replication scenarios to provide a
highly flexible and scalable replication environment. You can also use
fractional replication to restrict the attributes that are replicated
(e.g. if you don't want certain data to be present on a replica).

--snip--

Jon


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