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Re: WAL files during a backup

From: windsurferdrew-pg(at)yahoo(dot)com
To: steve(at)outtalimits(dot)com(dot)au
Cc: pgsql-admin(at)postgresql(dot)org
Subject: Re: WAL files during a backup
Date: 2008-08-28 12:24:56
Message-ID: 631740.57476.qm@web36904.mail.mud.yahoo.com (view raw or flat)
Thread:
Lists: pgsql-admin
Thanks Steve.

If I understand your comment regarding the 16MB limit, it means I should not worry about the WAL file not being copied to the archive directory.


I hope this also means a subsequent attempt to restore the db will successfully work since the WAL file is still in the pg_xlog directory.

Drew
 

----- Original Message ----
From: "steve(at)outtalimits(dot)com(dot)au" <steve(at)outtalimits(dot)com(dot)au>
To: windsurferdrew-pg(at)yahoo(dot)com
Cc: pgsql-admin(at)postgresql(dot)org
Sent: Wednesday, August 27, 2008 5:31:30 PM
Subject: Re: [ADMIN] WAL files during a backup

This WAL wont get copied to the archive directory until it reaches 16MB
worth of transactional data. I will actually be testing today for work, if
I can grab the latest xlog and this can be used in the restore aswell as
archived WAL's

I will let you know the results, unless some1 else already knows.?

On Wed, 27 Aug 2008 13:49:13 -0700 (PDT), windsurferdrew-pg(at)yahoo(dot)com
wrote:
> Steve, thanks for your response and your question.
> 
> Ok, here is some clarification on the WAL file name used in the example
> below.
> 
> The WAL file name I used in the example is actually
> 000000010000000000000088, and the backup file name is
> 000000010000000000000088.0089ED8C.backup.
> 
> The WAL file 000000010000000000000088 exists in the data/pg_xlog
directory
> after the backup run is completed. The problem for me is that it wasn't
> copied to the archive directory.
> 
> 
> Since this is a test machine and not much db activity occurring on this
> server, there have been 6 additional WAL files added to the pg_xlog
> directory in the last 6 hours since the last backup was performed.
> 
> Drew
> 
> 
> ----- Original Message ----
> From: "steve(at)outtalimits(dot)com(dot)au" <steve(at)outtalimits(dot)com(dot)au>
> To: windsurferdrew-pg(at)yahoo(dot)com
> Cc: pgsql-admin(at)postgresql(dot)org
> Sent: Wednesday, August 27, 2008 4:36:24 PM
> Subject: Re: [ADMIN] WAL files during a backup
> 
> 00000001000000000000223387  would usually be the next WAL to be written.
> How often are you WALs written out?
> 
> On Wed, 27 Aug 2008 07:07:17 -0700 (PDT), windsurferdrew-pg(at)yahoo(dot)com
> wrote:
>> I have a question regarding the WAL files that are moved during a backup
> to
>> the "archive directory".
>> 
>> I have setup the postgresql.conf file to have the following archive
>> command:
>> 
>> archive_command = 'cp -i %p /var/lib/pgsql/backups/%f </dev/null'
>> 
>> Environment: 
>> PG Version 8.1.4
>> OS: Linux 2.6.18-8.el5
>> 
>> After I have run the pg_hotbackup script, the backups directory contains
>> only 2 files:
>> 1. The gzipped tar file pg_hotbackup_<timestamp>.tar.gz, and
>> 2. a WAL file ".backup" file, (for example
>> 00000001000000000000223387.0089ED8C.backup)
>> 
>> The actual WAL file did not get copied to the backups directory. From
> the
>> example above, I would have expected at least 1  WAL file named
>> 00000001000000000000223387 to be in the backups directory.
>> 
>> My questions are:
>> 1. Is this normal behavior? (perhaps no activity in the DB to cause a
> WAL
>> file write during the backup?)
>> 2. If I try to restore the DB without this WAL file, will the restore
>> fail?
>> 
>> Thanks in advance
>> 
>> Drew 
>> 
>> 
>>


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