[prev in list] [next in list] [prev in thread] [next in thread]
List: slony1-general
Subject: Re: [Slony1-general] proper procedure for re-starting slony after
From: Geoffrey <lists () serioustechnology ! com>
Date: 2008-02-21 14:08:35
Message-ID: 47BD85E3.60600 () serioustechnology ! com
[Download RAW message or body]
Andrew Sullivan wrote:
> On Wed, Feb 20, 2008 at 07:13:37PM -0500, Geoffrey wrote:
>
>> thing I didn't mention is the actual configuration. Two boxes connected
>> to a single data silo. It's a hot/hot configuration. Separate
>> postmaster for each database. Half the postmasters run on one server,
>> the other half on the other. If/when one fails, the other picks up the
>> postmaster processes.
>
> How do you guarantee that the first is actually dead before the other "picks
> up the postmaster process"? I'm assuming what you mean is something like
> this:
>
> server1 <-------> disk <-------> server2
Correct. It's all handled by the Red Hat cluster software.
> Server1 and server2 are both attached to the disk at the same time. When
> server1 "goes away", server2 fires up a postgres instance on the same data
> area server1 was using, goes into recovery mode, and takes over the hostname
> and IP of server1.
Correct.
> In order for this to work, you have to be absolutely certain that server1 is
> dead and disconnected from the shared disk before server2 starts the
> postgres process on the same data area. Without that, you are sure to have
> database corruption of some kind. That is, the data from server1 MUST BE
> FLUSHED and on the platters before server2 starts using the same data area.
> So it might not be enough to be sure server1 is dead. You have to be sure
> the disk's cache is flushed too, or you could have a mess.
Agreed. We have tested this extensively. It's a moot point with regard
to our slony implementation as we've not had a failover since trying to
get slony implemented.
--
Until later, Geoffrey
Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety.
- Benjamin Franklin
_______________________________________________
Slony1-general mailing list
Slony1-general@lists.slony.info
http://lists.slony.info/mailman/listinfo/slony1-general
[prev in list] [next in list] [prev in thread] [next in thread]
Configure |
About |
News |
Add a list |
Sponsored by KoreLogic