Database Dumps and Backups

Database Dumps
and Backups
Karen Jex
February 2021

© Copyright EnterpriseDB Corporation, 2020. All rights reserved.
3
Agenda
• Why Take Backups?
• Why do we need to Recover?
• What are our Recovery Requirements?
• Backup Methods
• Backup Strategy
• Backup and Recovery Tools

4
Why Take Backups?
• Safeguard critical business data
• Recover from database failure
• Recovery strategy

5
Practice your disaster recovery
• The only way to be sure that a backup
can be restored is by restoring it
• If you need to restore a database,
it will be an emergency

6
Why do we need to Recover?
• Database server crash
• Storage array failure
• Batch process incorrectly modified data
• Human error (or willful destruction)
• Corrupted data file
• Creating development/test databases

7
What are our Recovery Requirements?
• Maximum Permitted Data Loss (RPO)
• Maximum Time to Recover (RTO)
• Backup Retention

Backups aren’t
the whole story

9
Physical Database Backup
• Offline
• Online
• Continuous archiving
• Storage snapshots
Backup Methods
Logical Database Backup

10
Physical Database Backups

11
Physical Database Backups
Advantages Disadvantages
• Generally faster to backup/restore from
than logical backup
• Allows PITR (if WALs are archived)
• Full or incremental backups
• Lack of flexibility
(backup/restore entire database cluster)

12
Offline Backups
(Physical Database Backups)
• Shut down database cluster
• Copy database files
• Start up database cluster

13
• Any file copy tool can be used
• No need to back up associated WAL files
• Database unavailable during the backup
• PITR is not possible
Offline Backups

14
• WAL = write-ahead log
• wal_level : minimal, replica (default) or logical
• archive_mode: off, on or always
• archive_command
WAL files

15
• Tell PostgreSQL you’re starting a backup
• Copy the database files
• Copy the WAL files
• Tell PostgreSQL you’ve finished the backup
Online Backups

16
• Database available during backup • WAL files must be backed up
• WAL parameters must be set correctly
Online Backups

17
• All WAL files are backed up
• Allows PITR
Continuous Archiving

18
Storage Snapshots

19
Storage Snapshots
• Consistent snapshot of the filesystem
• WAL files must be backed up
• Perform CHECKPOINT just before the snapshot
• Checkpoints of FS containing WAL and each tablespace must be simultaneous
• TEST

20
Logical Database Backups
my_db.dump

21
Logical Database Backups
• Flexibility
• Cross-version compatibility
• Slower restore than from physical
backup
• No PITR

22
Comparison of Backup Methods
Allows point in
time recovery
Database available
during backup
Allows backup of
individual objects
Offline Backup
Online Backup ✔
Continuous archiving ✔ ✔
Logical Backup/Dump ✔ ✔

23
Backup Strategy
• Backup method
• Frequency of backups
• Full or incremental backups
• Retention period

25
• Point in time recovery (PITR)
• Central backup architecture
• Scheduling
• Backup Catalogue
• Management of Backup and WAL files
Requirements of a Backup/Recovery Tool
• WAL archiving
• Monitoring and alerting
• Compression
• Incremental Backups
• Backup/restore of individual objects

26
Point in time recovery (PITR)
Sun Mon Tue Wed Thu Fri Sat
Backup 03:00 Batch 05:00 Backup 03:00 Backup 03:00 Batch 05:00
OLTP 09:00 - 18:00 OLTP 09:00 - 18:00 OLTP 09:00 - 18:00 OLTP 09:00 - 18:00 OLTP 09:00 - 18:00
Batch 22:00 Batch 22:00

27
Central Backup Architecture

28
Scheduling Backup
Catalogue

29
Management of Backup and WAL files WAL Archiving

30
Monitoring and Alerting Backup/Restore selected
objects

31
Compression Incremental Backups

33
Backup and Recovery Tools
Physical Backups Logical Backups
• pg_basebackup
• BART
• Barman
• pgBackRest
• pg_dump
• pg_dumpall
• pg_restore

34
No Backup Tool?

35
Custom Scripts
https://www.postgresql.org/docs/current/functions-admin.html#FUNCTIONS-ADMIN-BACKUP

36
pg_basebackup 1/2
https://www.postgresql.org/docs/current/app-pgbasebackup.html
• Does not affect other clients to the database
• Can be used for point-in-time recovery
• makes a binary copy of the database cluster files
• Puts system in and out of backup mode
• Backs up entire database cluster
• does not manage a backup library

37
pg_basebackup 2/2
# pg_basebackup -h mydbserver -z -D /my/backup/location/data

38
BART (EDB Backup and Recovery Tool) 1/2
EDB BART 2.6.1 User Guide

39
BART
2/2
# bart backup -s <server_name>
# bart restore -s <server_name>
# bart show-backups -s <server_name>

40
Barman 1/2
http://docs.pgbarman.org
● Remote backup and restore of multiple servers
● backup catalogs
● incremental backup
● retention policies
● archiving and compression of WAL files and backups
● rsync or PostgreSQL protocol

41
Barman 2/2
# barman backup <server_name>
# barman recover <server_name>
# barman list-backup <server_name>

42
pgBackRest 1/2
https://pgbackrest.org/
• Parallel Backup & Restore
• Local or Remote Operation
• Full, Incremental, & Differential Backups
• Backup Rotation & Archive Expiration
• Delta Restore
• Parallel, Asynchronous WAL Push & Get
• Tablespace & Link Support
• Encryption
• Limit restore to specific databases

43
pgBackRest 2/2
# pgbackrest stanza=<server_name> backup
# pgbackrest stanza=<server_name> restore
# pgbackrest stanza=<server_name> info

44
BART/BARMAN/pgBackRest
Common Architecture/Setup

45
• Create DB superuser for backups
• Create OS user for backups
• Allow DB connections from the backup server (pg_hba.conf )
• Allow passwordless connections between DB server and backup server
• Allow passwordless connection to DB from backup server

46
# backup_config_file
[global section]
backup location
database user
…
[server_name section]
hostname
data directory
…

47
/backup_home
server_name
archived_wals
backups
…

48
pg_dump
https://www.postgresql.org/docs/current/app-pgdump.html

49
pg_dump
https://www.postgresql.org/docs/current/app-pgdump.html

50
pg_dump
-F (--format)
c (custom)
d (directory)
t (tar)
-n schema
-t table

51
pg_dumpall
https://www.postgresql.org/docs/current/app-pg-dumpall.html

52
pg_restore
https://www.postgresql.org/docs/current/app-pgrestore.html

53
Comparison of Backup and Recovery Tools
PITR Scheduling
Management of
backup files
WAL archiving Monitoring
Centralised
architecture
BART ✔ via PEM ✔ ✔ via PEM ✔
Barman ✔ ✔ ✔ ✔ ✔ ✔
pgBackRest ✔ ✔ ✔ ✔
pg_dump
pg_dumpall

54
Comparison of Backup and Recovery Tools
Compression
Incremental
backups
Specific database /
schema / table
Global objects
Cross-version
compatibility
BART ✔ ✔ ✔
Barman ✔ ✔ ✔
pgBackRest ✔ ✔ Specific database ✔
pg_dump ✔ ✔ ✔
pg_dumpall ✔ ✔ ✔

55
Conclusions
• There is a vast array of different backup/export methods
and tools available but they all serve one main purpose,
and that is to support your recovery strategy.
• It is important to determine your recovery requirements
before implementing the backup strategy that fits your
specific needs.
• Your backup strategy may involve one or more of the
methods and tools that we have discussed.

56
Questions

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