Message-ID: <4D6146E9.2030302@2ndquadrant.com>
Date: Sun, 20 Feb 2011 11:52:57 -0500
From: Greg Smith <greg@2ndquadrant.com>
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To: Tony Nelson <tnelson@starpoint.com>
CC: pgsql-admin@postgresql.org
Subject: Re: Corrupted disk
References: <2B07A451-9F67-4438-8802-B10F46FDAF2E@starpoint.com>
In-Reply-To: <2B07A451-9F67-4438-8802-B10F46FDAF2E@starpoint.com>
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Tony Nelson wrote:
> I am ok, because I have a dump from last night, and wal since then.
>   

Dumps made with pg_dump are easy to restore from.  But they're fixed in 
time:  there is no applying WALs to them in order to update them.  
Anything that's happened to the server since then you can't add.

If you made a filesystem copy of the server using 
pg_start_backup/pg_stop_backup, and you save all of the WAL files after 
the backup began, that's also useful.  You can store from that backup 
and apply all the WAL that's happened since then.

> Can I drop/create/restore from this dump?  Or should I restore from last nights full and apply the WAL?
>   

If last night's backup with a filesystem one done with 
pg_start_backup/pg_stop_backup, and you have WAL since then, I would 
favor that set as likely to work fine.  But it sounds like what you have 
might instead be a pg_dump backup and some WAL files; you can't apply 
the WAL to such a dump. 

Whatever you do, you want to make a full filesystem copy of the server's 
data directory--with the server shutdown--before you do anything else.  
It's possible to recover from page errors and extract the available data 
using the right data recovery techniques, especially if there's a 
pg_dump available too; we offer some services in this area.  But if any 
serious changes are made to the database before we get to it, odds of 
successful recovery can drop fast.

-- 
Greg Smith   2ndQuadrant US    greg@2ndQuadrant.com   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support  www.2ndQuadrant.us
"PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books