[TriLUG] Slony-I

David Brain dbrain at gmail.com
Fri Feb 9 17:22:34 EST 2007


Thanks, the additional wrench in the works is that we're also looking
at a significant hardware change (32 to 64 bit OS) and also a version
change on the db (8.1 to 8.2) so a straight binary copy won't work.
Given the size of the DB a restore of a backup takes ~8hrs I can't see
any other way of doing it other than getting through the replication
issues.

David.

On 2/9/07, Jon Carnes <jonc at nc.rr.com> wrote:
> I don't have any experience that I know of with Slony-I, but I have
> backed up quite a number of ornery databases in my life.
>
> In a worse case scenario, you can mirror the HD that the DB runs on,
> using either hardware based or software based methods. Try doing it with
> an externally attached array or single HD. Once the mirroring is in
> place and running, you can pull the mirrored drive out put it on the
> shelf as a snap shot of the database up to that moment.
>
> Then hook up a fresh drive or array into the mirror and let the system
> re-mirror.  Swap in and out as necessary.
>
> If you have a secondary box with identical hardware, you can load the
> drive - repair the database (roll back any transactions that were
> stopped in mid process) and then backup the drive at your leisure.
>
> I've used this before for installs that *had* to be 24/7x52. Maintenance
> windows were 30 minutes once a year.
>
> We even rolled upgrades into the system using this method:
> Pull the mirror
> Rebuild the Database
> Upgrade
> Idle the current system
> Pull the transaction logs for the past two hours (the time it took for
> the upgrade) and apply those to the upgraded system.
> Put the new system in place for the old.
> Total down town = ~5minutes, 25 minutes to spare!
>
> Of course today we would simply use a cluster and do a rolling upgrade
> across the elements of the cluster (a rolling upgrade that sometimes
> takes two months to complete...)
>
> HtH - Jon
>
> On Thu, 2007-02-08 at 16:17 -0500, David Brain wrote:
> > Hi,
> >
> > Anyone have any experience with Slony-I.  I have a three  problems:
> >
> > 1. Large (100GB+) dataset to migrate
> > 2. Limited experience of Slony
> > 3. It's a production box, and in use 24/7
> >
> > I have tried to get replication working but have hit some issues with
> > writing data to the master db while the initial copy is running -
> > initially with a permission problem for one of the database users
> > trying to update one of the slony sequences.  Then once that was fixed
> > hit some problems with foreign key errors.
> >
> > I'll be at the meeting this evening if you'd rather talk about it
> > (which might  be faster..).
> >
> > Thanks,
> >
> > David.
>
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