Creating Storage Snapshots for PostgreSQL

To create a storage snapshot of the PostgreSQL cluster two system administration functions are used:

PostgreSQL 15 and later:

• pg_backup_start() - Prepares the server to begin an on-line backup. The only required parameter is an arbitrary user-defined label for the backup (Typically this would be the name under which the backup dump file will be stored.). If the optional second parameter is given as true, it specifies executing pg_backup_start as quickly as possible. This forces an immediate checkpoint which will cause a spike in I/O operations, slowing any concurrently executing queries.

• pg_backup_stop() - Finishes performing an on-line backup. The desired contents of the backup label file and the tablespace map file are returned as part of the result of the function and must be written to files in the backup area.

PostgreSQL 14 and earlier:

• pg_start_backup() - This prepares the cluster for an on-line backup. A label for the backup is provided during execution which can be used to identify it at a later date. Two modes of operation are possible when using this function , exclusive or non-exclusive mode.

• pg_stop_backup() - This the finishing function calls for an exclusive or non-exclusive backup. If exclusive mode was specified when using pg_start_backup then this function removes the backup label and table space mapping file.

Step 1. Prepare the system for a storage snapshot

The function can be started with the following arguments:

• PostgreSQL 14 and earlier - pg_start_backup(‘Snapshot Name' [, fast boolean [, exclusive boolean ]]).

• PostgreSQL 15 and later- pg_backup_start(‘Snapshot Name’, [, fast boolean]).

Executing pg_start_backup() will respond as follows if successful and respond with the write-ahead-log location:

• PostgreSQL 14 and earlier:

  postgres=# SELECT pg_start_backup('Snapshot01', true, true);
   pg_start_backup
  -----------------
   A/4F000028

• PostgreSQL 15 and later:

  postgres=# SELECT pg_backup_start('Snapshot01',false);
   pg_backup_start
  -----------------
   75/11000028

Step 2. Take a volume snapshot on FlashArray

Once the system has been prepared for a storage snapshot the volume(s) identified in Matching Storage Locations to FlashArray Volumescan have a storage snapshot created of them using the following process:

In the FlashArray graphical user interface find the volumes relevant to the PostgreSQL cluster. This can be done in the Storage view under Volumes.

Navigate to the Protection view and select Protection groups.

Identify the section for Source Protection Groups and select the "+" in the top right hand corner:

In the Create Protection Group dialog provide a unique name and select Create.

Once the Protection Group has been created it will show up in the Source Protection Groups section.

Selecting the Protection Group will bring up the context view for it. Identify the section for Members and select the three ellipses in the top right hand corner. In the selection options that emerge select Add Volumes... to add volumes or Add Hosts.. to add the PostgreSQL host in question.

In the Add Members dialog identify the relevant objects to add. Once complete select Add.

Once the relevant members have been added to the Protection Group identify the section for Protection Group Snapshots and select the "+" in the top right hand corner top create a protection group snapshot.

In the Create Snapshot dialog provide the same same label used in preparing the PostgreSQL for a storage snapshot as the Optional Suffix. At this point retention and replication policies can be applied to this specific storage snapshot. Select Create when ready to create the protection group snapshot.

Once the Protection Group Snapshot has been created it will be shown in the Protection Group Snapshots for the Protection Group.

Step 3. Stop the Backup Operation