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Message-ID: <1386366370.97863.YahooMailNeo@web162901.mail.bf1.yahoo.com>
Date: Fri, 6 Dec 2013 13:46:10 -0800 (PST)
From: Kevin Grittner <kgrittn@ymail.com>
Reply-To: Kevin Grittner <kgrittn@ymail.com>
Subject: Re: Cold backup with rsync -- WAL files?
To: Denish Patel <denish@omniti.com>, Craig James <cjames@emolecules.com>
Cc: Jeff Frost <jeff@pgexperts.com>, Payal Singh <payal@omniti.com>,
 "pgsql-admin@postgresql.org" <pgsql-admin@postgresql.org>
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Denish Patel <denish@omniti.com> wrote:
> Craig James <cjames@emolecules.com> wrote:
>> Jeff Frost <jeff@pgexperts.com> wrote:
>>>> Craig James <cjames@emolecules.com> wrote:
>>>>
>>>> After I rsync the postgres data directory, do I need the WAL
>>>> files from the source (they're on a separate disk, not part of
>>>> the postgres data directory)?=A0 Can/should=A0 I erase the WAL
>>>> directory of the destination?
>>>
>>> Yes, you need the WAL files.
>>
>> Now I have two directly conflicting answers.=A0 You say the WAL
>> files are needed even though the DB is shut off, and Payal Singh
>> says I don't need the WAL files (but I don't think he cc'd the
>> mailing list).
>>
>> Why are the WAL files necessary if the DB is shut off?=A0 Why
>> can't they just be erased?
>>
>> It's a gigabyte of copying that I was hoping to avoid.

> Payal is right. You don't need WAL for Cold backup.

This experiment took far less time than reading the thread:

kgrittn@Kevin-Desktop:~/pg/master$ pg_ctl -D Debug/data -m fast -w stop
waiting for server to shut down.... done
server stopped
kgrittn@Kevin-Desktop:~/pg/master$ mkdir Debug/data/xlog2
kgrittn@Kevin-Desktop:~/pg/master$ mv Debug/data/pg_xlog/* Debug/data/xlog2/
kgrittn@Kevin-Desktop:~/pg/master$ rm -f Debug/data/logfile ; pg_ctl -D Deb=
ug/data -l Debug/data/logfile -w start || cat Debug/data/logfile
waiting for server to start........ stopped waiting
pg_ctl: could not start server
Examine the log output.
LOG:=A0 database system was shut down at 2013-12-06 15:31:27 CST
LOG:=A0 creating missing WAL directory "pg_xlog/archive_status"
LOG:=A0 invalid primary checkpoint record
LOG:=A0 invalid secondary checkpoint record
PANIC:=A0 could not locate a valid checkpoint record
LOG:=A0 startup process (PID 15471) was terminated by signal 6: Aborted
LOG:=A0 aborting startup due to startup process failure

Now, if you're very clever you might be able to copy just
*selected* WAL files.=A0 You've gotta ask yourself a question: "Do I
feel lucky?"=A0 Well, do ya?=20

--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company


--=20
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