This talk cover various advanced topics in the area of backups: - incremental backups; - archive management; - backup validation; - retention policies; etc. Based on these features, we'll compare various backup/recovery solutions for PostgreSQL. This information will help you to choose the most appropriate tool for your system.

1. Advanced PostgreSQL
backup & recovery
methods
Anastasia Lubennikova
Postgres@CERN 2020
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2. Agenda
- Why backup?
- What is a good backup tool?
- Overview of advanced backup features
- Overview of PostgreSQL backup tools
Spoiler: this talk doesn’t contain any benchmarks.
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3. Why do you need a backup?
- To restore the database after an accident
- hardware failure
- software bug
- human error
- To set up a new replica
- To create a test environment
- To inspect data from the past
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4. What are the options?
- replica is not a backup
- dump a.k.a. “logical backup”
- storage snapshots
- pg_basebackup
- set of custom scripts
- PostgreSQL specific backup tools
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5. What makes a good backup tool?
- Convenience
- out-of-box automatization of various routines
- documentation & support
- convenient and stable api
- Performance
- parallel execution
- compression
- incremental & differential backups
- WAL prefetch
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6. What backup tools exist?
- Barman
- pgBackRest
- pg_probackup
- WAL-G
- BART
- part of the “EDB Advanced Server”
- requires pg_basebackup
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7. Who is who? Barman
- https://www.pgbarman.org/
- 2ndQuadrant
- GPL v 3.0
- Python
- first release: 2011
- Two methods: basebackup & rsync
Notable features:
Synchronous streaming for “zero data loss”.
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8. Who is who? pgBackRest
- https://pgbackrest.org/
- Crunchy Data
- MIT License
- C
- first release: 2014
Notable features:
Performance optimizations for large backups.
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9. Who is who? pg_probackup
- https://github.com/postgrespro/pg_probackup
- Postgres Professional
- PostgreSQL License
- C
- first release: 2017 (based on pg_arman)
Notable features:
Page-level incremental backups and built-in validation.
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10. Who is who? WAL-G
- https://github.com/wal-g/wal-g
- introduced by Citus Data,
now maintained by Yandex Cloud team
- Apache License, Version 2.0
- Go
- first release: 2017 ( “based on” WAL-E)
Notable features:
Out-of-box support for various cloud storages.
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11. Feature list
1. Documentation & Support
2. Backup management
3. WAL archive management
4. Incremental backups
5. Compression and parallel execution
6. Remote backup
7. Cloud backup
8. Advanced restore options
9. Backup validation
10. Backup retention
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12. 1. Documentation & Support
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13. Documentation
Barman User guide & command reference.
Great overview of backup architectures
pgBackRest User guide & command reference
pg_probackup User guide & command reference
WAL-G README
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14. Installation
Barman Linux packages, Build from source
pgBackRest Linux packages, Build from source
pg_probackup Linux packages, Build from source,
Windows installer
WAL-G Linux binary, Build from source
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15. Support: bug fixes
Barman https://github.com/2ndquadrant-it/barman/issues
pgBackRest https://github.com/pgbackrest/pgbackrest/issues
pg_probackup https://github.com/postgrespro/pg_probackup/issues
WAL-G https://github.com/wal-g/wal-g/issues
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16. Commercial support
Barman 2ndQuadrant
pgBackRest CrunchyData
pg_probackup Postgres Professional
WAL-G
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17. 2. Backup management
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18. Set up new PostgreSQL instance
Barman server
configuration files
pgBackRest stanza
configuration files
pg_probackup instance
configuration files, set-config command
WAL-G -
config via environment variables
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19. Backup information
Barman plain
pgBackRest plain, json
+ postgresql table
pg_probackup plain, json
+ detailed wal archive info
WAL-G plain, json
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20. 3. WAL archive management
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21. WAL archive management
Barman rsync / get-wal
pgBackRest archive-push / archive get
archive-async
pg_probackup archive-push / archive-get
WAL-G wal-push / wal-fetch
wal prefetch
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22. Streaming backups
- Recovery Point Objective (RPO):
"maximum targeted period in which data might be lost
from an IT service due to a major incident"
- “RPO = 0” (Zero data loss)
can be achieved by synchronous WAL streaming
- replication slot
prevents the removal of WAL that is not yet received
(PostgreSQL feature)
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23. Streaming backups
Barman streaming_archiver (pg_recievewal)
replication slot
pgBackRest
pg_probackup backup --stream
replication slot
WAL-G
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24. 4. Incremental backups
Full backup includes all data files.
Differential backup contains changes since last full backup.
Incremental backup contains changes since last backup.
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25. Incremental backup methods
- DELTA - read everything, backup what changed
- independent method
- read load on data server
- PAGE - scan WAL to determine changed blocks
- requires WAL archive
- minimal load on data server
- PTRACK - remember changed blocks in a map
- requires core patch
- minimal load during backup
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26. Incremental backups
Barman file-level incremental (DELTA)
pgBackRest file-level incremental (DELTA)
file-level differential (DELTA)
pg_probackup page-level incremental:
DELTA, PAGE, PTRACK
WAL-G page-level incremental (DELTA)
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27. 5. Compression and parallel execution
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28. 6. Remote backup
Barman SSH
pgBackRest SSH
pg_probackup SSH
WAL-G
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29. 7. Cloud backup
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30. Backup to cloud storage
Barman scripts to ship backups to S3
pgBackRest Amazon S3
+ encryption
pg_probackup
WAL-G Amazon S3, Google Cloud Storage,
Azure Storage, Swift Object Storage
+ encryption
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31. Extra backup features
- Backup from standby (All tools)
- to reduce load on master data server
- Resume backup (only pgBackRest)
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32. 8. Advanced restore options. PITR
Restore to a certain moment in time.
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33. Point-in-time-recovery
Barman recovery target options
pgBackRest recovery target options
pg_probackup recovery target options
WAL-G
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34. Partial restore
Barman
pgBackRest restore selected databases
pg_probackup restore selected databases
WAL-G
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35. 9. Backup validation
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36. Validate backups
Barman DIY with custom hooks
on backup & restore
pgBackRest page checksums on backup
pg_probackup page checksums on backup
validate on demand
check instance
WAL-G
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37. 10. Backup retention
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38. 10. Backup retention. Redundancy = 3
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39. 10. Backup retention. Window = 7 days
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40. Retention policy
Barman retention_policy = REDUNDANCY
retention_policy = RECOVERY WINDOW
pgBackRest redundancy
pg_probackup --retention-redundancy
--retention-window
WAL-G redundancy: retain N
window: delete before
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41. Backup pinning
Barman
pgBackRest
pg_probackup ttl=0
WAL-G backup-mark
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42. Archive retention
Barman
pgBackRest Archive Retention
--repo-retention-archive
pg_probackup delete --expired --wal
--wal-depth=1
WAL-G
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43. Backup merging
Save space by merging old incremental backups.
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44. Backup merging
Barman
pgBackRest
pg_probackup merge
--merge-expired
WAL-G
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46. Conclusion
Barman
(rsync)
pgBackRest pg_probackup WAL-G
Support + + + +
Backup management + + + -
WAL management + + + +
Incremental backup + + + +
Compression &
parallel execution
+ + + +
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47. Conclusion
Barman
(rsync)
pgBackRest pg_probackup WAL-G
Remote backup + + + +
Cloud backup - + - +
Advanced restore + + + -
Backup validation + + + -
Backup retention + + + +
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