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Re: WAL to RAW devices ?

From: "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>
To: Alex Vinogradovs <AVinogradovs(at)clearpathnet(dot)com>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: WAL to RAW devices ?
Date: 2007-09-01 00:45:47
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Lists: pgsql-general
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Alex Vinogradovs wrote:
> Hi guys,
> I've got a bunch of PosgreSQL servers connected to external storage,
>  where a single server needs to be serving as WO database dealing with
> INSERTs only, and bunch of other guys need to obtain a copy of that
> data for RO serving, without taking resources on WO server.

You can't do that with PostgreSQL without replication. Unless you are
willing to have outages with your RO servers to apply the logs.

Further you are considering the wrong logs. It is not the WAL logs, but
the archive logs that you need.


Joshua D. Drake

>  The idea is to have say 2 raw devices which would be used as 2 WAL
> segments (round-robin). RO servers will go after the one that's not used
> at a given time with something like xlogdump utility and produce INSERT
> statements to be then executed locally. After that import is done, a
> command will be issued to the WO server to switch to the other segment
> so that the cycle can repeat.
>  The objective of that replication model is to ensure that SELECT
> queries won't ever affect the performance of the WO server,
> which may experience uneven loads.
> Is that possible with the 8.2.4 or 8.3 capabilities, or maybe with
> minor modifications ?
> Thanks!
> Best regards,
> Alex Vinogradovs
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