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Re: PostgreSQL Migration of databases 7.2 to 7.4

From: Christopher Browne <cbbrowne(at)acm(dot)org>
To: pgsql-admin(at)postgresql(dot)org
Subject: Re: PostgreSQL Migration of databases 7.2 to 7.4
Date: 2004-08-24 17:04:38
Message-ID: m3hdqso4bd.fsf@wolfe.cbbrowne.com (view raw or flat)
Thread:
Lists: pgsql-admin
Quoth "Mario Thomas" <mario(at)alamar(dot)net>:
> We have a server in our datacentre running PostgreSQL 7.2 with about 50
> databases set up (for different customers). We have just commissioned a
> much better specified server which is running PostgreSQL 7.4.
>
> We need to migrate the databases from 7.2 to 7.4. The smallest database
> contains about 200K of data whilst the largest database weighs in at
> about 100Mb.
>
> What's the best way to migrate the data? Would you suggest using the
> pgdump tools? We've found them to be quite problematic in use and are
> not entirely sure of the best command line switches to use.
>
> We need to make sure the data and permissions get migrated, as the data
> is being used for live web sites. So obviously speed of migration is
> important as we will have a period of downtime to complete the
> migrations.

The way to minimize the downtime is to use one of the replication
systems to replicate data between two database instances.  It may take
a while to set up the replica, but once it is in place, if you keep it
fairly up to date, the switchover between versions should just take
the few minutes needed to:

 a) Stop new data from going into the old database;
 b) Allowing all updates to get to the new database;
 c) Switching access over to the new database.

Unfortunately, the "latest and greatest" option, Slony-I, does not
support versions younger than 7.3.3, so you'd have to look at other
solutions such as ERServer.

Earlier in the year, this approach was used at Afilias, in conjunction
with ERServer, to migrate systems from 7.2.4 to 7.4.2.
-- 
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