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DOC: improve checkb docs and fix some other minor issues

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Liudmila Mantrova
2019-11-25 19:24:29 +03:00
parent b3be139456
commit 10c1f7ad3f
1 changed files with 47 additions and 50 deletions
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doc/pgprobackup.xml
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@@ -189,10 +189,12 @@ doc/src/sgml/pgprobackup.sgml
<itemizedlist spacing="compact">
<listitem>
<para>
Incremental backup: page-level incremental backup allows you
to save disk space, speed up backup and restore. With three
different incremental modes, you can plan the backup strategy
in accordance with your data flow.
Incremental backup: with three different incremental modes,
you can plan the backup strategy in accordance with your data flow.
Incremental backups allow you to save disk space
and speed up backup as compared to taking full backups.
It is also faster to restore the cluster by applying incremental
backups than by replaying WAL files.
</para>
</listitem>
<listitem>
@@ -296,9 +298,11 @@ doc/src/sgml/pgprobackup.sgml
</listitem>
<listitem>
<para>
Incremental backups only store the data that has changed since
the previous backup. It allows to decrease the backup size and
speed up backup and restore operations. <application>pg_probackup</application> supports
Incremental backups operate at the page level, only storing the data that has changed since
the previous backup. It allows you to save disk space
and speed up the backup process as compared to taking full backups.
It is also faster to restore the cluster by applying incremental
backups than by replaying WAL files. <application>pg_probackup</application> supports
the following modes of incremental backups:
</para>
<itemizedlist spacing="compact">
@@ -306,7 +310,7 @@ doc/src/sgml/pgprobackup.sgml
<para>
DELTA backup. In this mode, <application>pg_probackup</application> reads all data
files in the data directory and copies only those pages
that have changed since the previous backup. Note that this
that have changed since the previous backup. This
mode can impose read-only I/O pressure equal to a full
backup.
</para>
@@ -1047,7 +1051,7 @@ GRANT SELECT ON TABLE pg_catalog.pg_database TO backup;
<para>
<literal>postgres</literal> is the OS user on
<literal>db_host</literal> used to start the <productname>PostgreSQL</productname>
cluster. Note that for <productname>PostgreSQL</productname> 11 or higher a
cluster. For <productname>PostgreSQL</productname> 11 or higher a
more secure approach can be used thanks to
<ulink url="https://postgrespro.com/docs/postgresql/current/app-initdb.html#APP-INITDB-ALLOW-GROUP-ACCESS">allow-group-access</ulink>
feature.
@@ -1390,52 +1394,46 @@ pg_probackup backup -B <replaceable>backup_dir</replaceable> --instance <replace
<refsect2 id="pbk-verifying-a-cluster">
<title>Performing Cluster Verification</title>
<para>
To verify that <productname>PostgreSQL</productname> database cluster is free of
corruption, run the following command:
To verify that <productname>PostgreSQL</productname> database cluster is
not corrupt, run the following command:
</para>
<programlisting>
pg_probackup checkdb [-B <replaceable>backup_dir</replaceable> [--instance <replaceable>instance_name</replaceable>]] [-D <replaceable>data_dir</replaceable>]
pg_probackup checkdb [-B <replaceable>backup_dir</replaceable> [--instance <replaceable>instance_name</replaceable>]] [-D <replaceable>data_dir</replaceable>] [<replaceable>connection_options</replaceable>]
</programlisting>
<para>
This command performs physical verification works similar to
<link linkend="pbk-page-validation">page validation</link> that is
done during backup with several differences:
This command performs physical verification of all data files
located in the specified data directory by running page header
sanity checks, as well as block-level checksum verification if checksums are enabled.
If a corrupt page is detected, <command>checkdb</command>
continues cluster verification until all pages in the cluster
are validated.
</para>
<itemizedlist spacing="compact">
<listitem>
<para>
<command>checkdb</command> is read-only.
</para>
</listitem>
<listitem>
<para>
Even if a corrupt page is detected, <command>checkdb</command>
continues cluster verification until all pages in the cluster
are validated.
</para>
</listitem>
<listitem>
<para>
<command>checkdb</command> does not strictly require
<emphasis>the backup catalog</emphasis>, so it can be used
to verify database clusters that are
<emphasis role="strong">not</emphasis>
<link linkend="pbk-adding-new-backup-instance">added to the
backup catalog</link>.
</para>
</listitem>
</itemizedlist>
<para>
If <replaceable>backup_dir</replaceable> and
<replaceable>instance_name</replaceable> are omitted,
By default, similar <link linkend="pbk-page-validation">page validation</link>
is performed automatically while a backup is taken by
<application>pg_probackup</application>. The <literal>checkdb</literal>
command enables you to perform such page validation
on demand, without taking any backup copies, even if the cluster
is not backed up using <application>pg_probackup</application> at all.
</para>
<para>
To perform cluster verification, <application>pg_probackup</application>
needs to connect to the cluster to be verified. In general, it is
enough to specify the backup instance of this cluster for
<application>pg_probackup</application> to determine the required
connection options. However, if <literal>-B</literal> and
<literal>--instance</literal> options are ommitted, you have to provide
<link linkend="pbk-connection-opts">connection options</link> and
<replaceable>data_dir</replaceable> must be provided via environment
<replaceable>data_dir</replaceable> via environment
variables or command-line options.
</para>
<para>
Physical verification cannot detect logical inconsistencies,
missing and nullified blocks or entire files, repercussions from
<productname>PostgreSQL</productname> bugs and other wicked anomalies. Extensions
missing or nullified blocks and entire files, or similar anomalies. Extensions
<ulink url="https://postgrespro.com/docs/postgresql/current/amcheck.html">amcheck</ulink>
and
<ulink url="https://github.com/petergeoghegan/amcheck">amcheck_next</ulink>
@@ -1448,7 +1446,7 @@ pg_probackup checkdb [-B <replaceable>backup_dir</replaceable> [--instance <repl
the <xref linkend="pbk-checkdb"/> command:
</para>
<programlisting>
pg_probackup checkdb -D <replaceable>data_dir</replaceable> --amcheck
pg_probackup checkdb -D <replaceable>data_dir</replaceable> --amcheck [<replaceable>connection_options</replaceable>]
</programlisting>
<para>
You can skip physical verification by specifying the
@@ -1929,8 +1927,9 @@ pg_probackup backup -B <replaceable>backup_dir</replaceable> --instance <replace
<para>
For example, <xref linkend="pbk-backup"/> and
<xref linkend="pbk-checkdb"/> commands use a regular
<productname>PostgreSQL</productname> connection. To avoid specifying these options each
time on the command line, you can set them in the
<productname>PostgreSQL</productname> connection. To avoid specifying
<link linkend="pbk-connection-opts">connection options</link>
each time on the command line, you can set them in the
<filename>pg_probackup.conf</filename> configuration file using the
<xref linkend="pbk-set-config"/> command.
</para>
@@ -2882,12 +2881,10 @@ BACKUP INSTANCE 'node'
node 10 P7XDQV 2019-04-08 05:32:59+03 PAGE STREAM 1/0 11s 19MB 16MB 1.0 0/15000060 0/15000198 OK
node 10 P7XDJA 2019-04-03 05:28:36+03 FULL STREAM 1/0 21s 32MB 16MB 1.0 0/13000028 0/13000198 OK
</programlisting>
<note>
<para>
The <literal>Time</literal> field for the merged backup displays the time
required for the merge.
</para>
</note>
</refsect3>
<refsect3 id="pbk-backup-pinning">
<title>Backup Pinning</title>
@@ -3122,7 +3119,7 @@ pg_probackup delete -B <replaceable>backup_dir</replaceable> --instance <replace
pg_probackup delete -B <replaceable>backup_dir</replaceable> --instance <replaceable>instance_name</replaceable> --delete-expired
</programlisting>
<para>
Note that expired backups cannot be removed while at least one
Expired backups cannot be removed while at least one
incremental backup that satisfies the retention policy is based
on them. If you would like to minimize the number of backups
still required to keep incremental backups valid, specify the