Re: Moving pg_xlog folder

On Sun, Jun 28, 2015 at 12:19 AM, Wei Shan <weishan(dot)ang(at)gmail(dot)com> wrote:

> Hi all,
>
> OS: CentOS
> PG version: 9.3
>
> I'm testing the scenario of moving the xlog folder to a fast pair of disk.
> This was the steps I followed;
>
> 1. create new mountpoint with the correct permissions
> 2. Shutdown DB
> 3. Create softlink from new mountpoint to $PG_DATA/pg_xlog
> 4. Startup DB
>
>
​If I understand here correctly, you want to move $PGDATA/pg_xlog to
"/fast/disk/pg_xlog" directory.

If I want to implement the same on my local machine of moving of pg_xlog to
other directory (in your case other mount point). I will follow below steps:

1) Stop the running cluster

-bash-4.2$ pwd
/opt/PostgreSQL/9.4
/opt/PostgreSQL/9.4/bin/pg_ctl -D /opt/PostgreSQL/9.4/data/ stop -mf

2) Create a new directory (In your case new mount point with correct
permission)

mkdir temp_pgxlog

3) Copy existing files and directory from current $PGDATA/pg_xlog to new
mount point directory.

cp -rf /opt/PostgreSQL/9.4/data/pg_xlog/* /opt/PostgreSQL/9.4/temp_pgxlog/

4) Create symbolic link to new directory by renaming existing directory.

cd /opt/PostgreSQL/9.4/data/
mv pg_xlog/ pg_xlog_bkp
ln -s ~/temp_pgxlog/ pg_xlog

5) Start the cluster.

/opt/PostgreSQL/9.4/bin/pg_ctl -D /opt/PostgreSQL/9.4/data/ start

However, after I start the DB, I hit the following error;
>
> *-bash-4.1$ psql*
>
> *psql: could not connect to server: No such file or directory*
>
> * Is the server running locally and accepting*
>
> * connections on Unix domain socket "/tmp/.s.PGSQL.5432"?*
>
> This issue resolves by itself once I reboot the server after I move the
> XLOG. Any ideas what I did wrongly?
>
> Thanks!
> --
> Regards,
> Ang Wei Shan
>

​Reboot of the server not required, have you check below areas before
rebooting.

1) Is symbolic link of $PGDATA/pg_xlog pointing to new location ?

2) What information you see in the Database server logs ?

​---
Regards,
Raghavendra
EnterpriseDB Corporation
Blog: http://raghavt.blogspot.com/