Re: Needs discussion of pg_xlog

On 12/01/2016 07:00 AM, robert@interactive.co.uk wrote:
> The following documentation comment has been logged on the website:
>
> Page: https://www.postgresql.org/docs/9.4/static/runtime-config-file-locations.html
> Description:
>
> In various places (e.g. stackoverflow), I've seen people suggest having
> pg_xlog ion a different disk (i.e. not in /var/lib/pgsql/9.X/data).
>
> The only mention of this that I've seen is in Section 29.5 (WAL Internals),
> and that just says "it is advantageous...", with no explanation.
>
> If this IS a good idea, then "Server Configuration / File Locations" is
> where it should be discussed: in particular, why is it a good idea, and how
> does it affect backups (and in particular base backups to a standby server).

The reason it can be advantageous is that pg_xlog has a different write
profile that $PGDATA. The WAL is written sequentially versus randomly.

JD


>


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