A quick synopsis of Backup-Recovery in PostgreSQL - Logical Backup, Physical Backup and PITR

1. Backup-Recovery
in PostgreSQL
Logical Backup, Physical Backup and PITR
15/7/2013

2. Available Backup and Recovery Tools
•
•
•
•
•
pg_basebackup
Compressed backup
Recovery with WAL and archived WAL
Recover to the point of crash
Point in Time Recover to recover from data corruption due to a bad query/batch
CONFIDENTIAL
© 2012 EnterpriseDB. All rights reserved.
Confidential information, for internal use only
Physical and Logical Backup
Logical Backup using pg_dump
Instance level logical backup using pg_dumpall
Table level, Schema level or DB level logical backup
Different file formats available for pg_dump backup
pg_restore to restore binary backup with pg_dump
Physical Backups
2

3. Online Backup
 Enable Archiving
Confidential information, for internal use only
• archive_command = 'cp %p /mnt/server/archivedir/%f‘
• wal_level = archive
• Archive_mode = on
 Take a backup
• SELECT pg_start_backup('label');
• Take a backup (file system level copy)
• SELECT pg_stop_backup();
 Alternative to Manual backup: Use pg_basebackup for taking a backup
•
pg_basebackup -D /opt/PostgresPlus/9.2AS/data -h 192.168.160.147 -W -p 5444 -Fp --xlogmethod=stream
3

4. Recovery: Restore the server
Confidential information, for internal use only
 Stop the server, if it's running. Change the
pg_hba.conf to disallow user’s login during recovery
 Keep a backup of original server or at least pg_xlog
 Restore the database files from your file system
backup. Be sure about the ownership and soft links
4

5. Recovery: Prepare the Server
 Remove any files present in pg_xlog/;
Confidential information, for internal use only
 If you have unarchived WAL segment files that you saved (step 2), copy them into
pg_xlog/
 Create a recovery command file recovery.conf in the cluster data directory:
• restore_command = 'cp /mnt/server/archivedir/%f "%p" '
 If this is a point in time recovery to recover from a bad batch operation or a bad
command which has corrupted the data then add recovery_target_time to a timestamp
which is just before the bad command/batch was fired
• recovery_target_time = '18-JUL-13 23:07:05.39855'
5

6. Start the Recovery
 Start the server
Confidential information, for internal use only
• The server will go into recovery mode and proceed to read through the archived
WAL files it needs
• Should the recovery be terminated because of an external error, the server can
simply be restarted and it will continue recovery
• Upon completion of the recovery process, the server will rename recovery.conf to
recovery.done
 Inspect the contents of the database to ensure you have
recovered to the desired state. If not, restart the whole
process
6

7. Sameer Kumar
Ashnik Pte Ltd, Singapore
www.ashnik.com | sameer.kumar@ashnik.com
7