Message-ID: <49ADD08C.3000604@srce.hr>
Date: Wed, 04 Mar 2009 01:51:24 +0100
From: Jakov Sosic <jakov.sosic@srce.hr>
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To: pgsql-admin@postgresql.org
Subject: Re: Backing up postgresql database
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Scott Marlowe wrote:

> That might not be much smaller if you're doing a lot of updates /
> inserts / deletes.  Also, SQL ain't the same as what was committed. If
> you insert now() it won't be the same when you run it in two days.

Well I think I miscalculated a little bit... It's more like a 120 GB per
day, not 5TB... I'll post correct results tommorow.


> The key here is it seems like you have a very high churn rate, and if
> you're backup solution involves saving all those changes and applying
> them later, it's gonna incur a rather large storage use.
> 
> I.e. PITR, as you have it implemented, might not be your best solution.


> You might be better off with something like Slony, Burcado (sp?) or
> another of other live replication setups that don't have the same
> issues you're seeing here.

Replication involves another machine, and more load on current one, and
that's not what I want.


> It's probably better to keep pg_dump type backups for those types of
> things.  pitr is a poor challenger to the easily compressed output of
> pg_dump for offsite backups.  Especially over a wire.

But how long would pg_dump execute on DB with this volume of traffic?
And would it kill the machine in that period? I can try that as well
tommorow...


> If I update a single row in a database 1,000,000,000 times, how man
> WAL files will you need?
> If you update every row in a 1,000,000,000 row database, how many WAL
> files will you need?

Obviously application is not just appending new data, as I thought
before... Because appends (aka INSERT) wouldn't cause this volume of
WAL's or would it?


> I'm wondering what you're objectives are in your backup strategy, it
> might be you're coming at it one way when we'd all approach it from
> another way.  Or not.

You are correct on this one. DB I'm talking about is not that important
to have rigorous backup schedule and recovery policies. I rather have
hardware limitations and I have to find the best solution to not
overutilize the hardware and in the same time have as frequent backups
as possible.


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