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docs: improve pg_upgrade standby instructions

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This makes it clear that pg_upgrade standby upgrade instructions should
only be used in link mode, adds examples, and explains how rsync works
with links.

Reported-by: Andreas Joseph Krogh

Discussion: https://postgr.es/m/VisenaEmail.6c.c0e592c5af4ef0a2.15e785dcb61@tc7-visena

Backpatch-through: 9.5
This commit is contained in:
Bruce Momjian 2017-09-13 09:11:28 -04:00
parent 8d787bd66c
commit 3b3327ef27
1 changed files with 41 additions and 23 deletions
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64
doc/src/sgml/ref/pgupgrade.sgml
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@ -423,10 +423,12 @@ pg_upgrade.exe
<para> <para>
If you have Streaming Replication (see <xref If you have Streaming Replication (see <xref
linkend="streaming-replication">) or Log-Shipping (see <xref linkend="streaming-replication">) or Log-Shipping (see <xref
linkend="warm-standby">) standby servers, follow these steps to linkend="warm-standby">) standby servers, and used link mode,
upgrade them. You will not be running <application>pg_upgrade</> follow these steps to upgrade them. You will not be running
on the standby servers, but rather <application>rsync</> on the <application>pg_upgrade</> on the standby servers, but rather
primary. Do not start any servers yet. <application>rsync</> on the primary. Do not start any servers yet.
If you did <emphasis>not</> use link mode, skip the instructions in
this section and simply recreate the standby servers.
</para> </para>
<substeps> <substeps>
@ -482,9 +484,11 @@ pg_upgrade.exe
<title>Run <application>rsync</></title> <title>Run <application>rsync</></title>
<para> <para>
From a directory on the primary server that is above the old and When using link mode, standby servers can be quickly upgraded using
new database cluster directories, run this on the <application>rsync</>. To accomplish this, from a directory on
<emphasis>primary</> for each standby server: the primary server that is above the old and new database cluster
directories, run this on the <emphasis>primary</> for each standby
server:
<programlisting> <programlisting>
rsync --archive --delete --hard-links --size-only old_pgdata new_pgdata remote_dir rsync --archive --delete --hard-links --size-only old_pgdata new_pgdata remote_dir
@ -492,30 +496,44 @@ rsync --archive --delete --hard-links --size-only old_pgdata new_pgdata remote_d
where <option>old_pgdata</> and <option>new_pgdata</> are relative where <option>old_pgdata</> and <option>new_pgdata</> are relative
to the current directory on the primary, and <option>remote_dir</> to the current directory on the primary, and <option>remote_dir</>
is <emphasis>above</> the old and new cluster directories on is <emphasis>above</> the old and new cluster directories
the standby. The old and new relative cluster paths on the standby. The directory structure under the specified
must match on the primary and standby server. Consult the directories on the primary and standbys must match. Consult the
<application>rsync</> manual page for details on specifying the <application>rsync</> manual page for details on specifying the
remote directory, e.g. <literal>standbyhost:/opt/PostgreSQL/</>. remote directory, e.g.
<programlisting>
rsync --archive --delete --hard-links --size-only /opt/PostgreSQL/9.5/data \
/opt/PostgreSQL/9.6/data standby.example.com:/opt/PostgreSQL
</programlisting>
</para> </para>
<para> <para>
What <application>rsync</> does is to copy files from the What this does is to record the links created by
primary to the standby, and, if <application>pg_upgrade</>'s <application>pg_upgrade</>'s link mode that connect files in the
<option>--link</> mode was used, link files from the old to old and new clusters on the primary server. It then finds matching
new clusters on the standby. It links the same files that files in the standby's old cluster and creates links for them in the
<application>pg_upgrade</> linked in the primary old and new standby's new cluster. Files that were not linked on the primary
clusters. (Of course, linking speeds up <application>rsync</>.) are copied from the primary to the standby. (They are usually
Unfortunately, <application>rsync</> needlessly copies files small.) This provides rapid standby upgrades. Unfortunately,
associated with temporary and unlogged tables because these files <application>rsync</> needlessly copies files associated with
don't normally exist on standby servers. temporary and unlogged tables because these files don't normally
exist on standby servers.
</para> </para>
<para> <para>
If you have tablespaces, you will need to run a similar If you have tablespaces, you will need to run a similar
<application>rsync</> command for each tablespace directory. If you <application>rsync</> command for each tablespace directory, e.g.:
have relocated <filename>pg_xlog</> outside the data directories,
<application>rsync</> must be run on those directories too. <programlisting>
rsync --archive --delete --hard-links --size-only /vol1/pg_tblsp/PG_9.5_201510051 \
/vol1/pg_tblsp/PG_9.6_201608131 standby.example.com:/vol1/pg_tblsp
</programlisting>
If you have relocated <filename>pg_xlog</> outside the data
directories, <application>rsync</> must be run on those directories
too.
</para> </para>
</step> </step>