Thread: pgsql: Document that a CHECKPOINT before taking a file system snapshot
Document that a CHECKPOINT before taking a file system snapshot can reduce recovery time. Branch ------ master Details ------- http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=7276ab5888d85782d988fc297ad2e176c7ad1bca Modified Files -------------- doc/src/sgml/backup.sgml | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-)
Re: pgsql: Document that a CHECKPOINT before taking a file system snapshot
From
Cédric Villemain
Date:
2010/11/25 Bruce Momjian <bruce@momjian.us>: > Document that a CHECKPOINT before taking a file system snapshot can > reduce recovery time. I didn't follow that on -hackers, but : * checkpoint take place in the pg_start_backup process (before it releases the hand, so before you can start snapshoting) * we used to issue a checkpoint *before* pg_start_backup to reduce pg_start_backup duration in case you have wal_archiving turn off and full_page_write is off, it reduces a bit the IO contention. (or even if not I hate seing this pg_start_backup taking seconds/minutes to finish) How the checkpoint before will reduce recovery time ? > > Branch > ------ > master > > Details > ------- > http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=7276ab5888d85782d988fc297ad2e176c7ad1bca > > Modified Files > -------------- > doc/src/sgml/backup.sgml | 2 ++ > 1 files changed, 2 insertions(+), 0 deletions(-) > > > -- > Sent via pgsql-committers mailing list (pgsql-committers@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-committers > -- Cédric Villemain 2ndQuadrant http://2ndQuadrant.fr/ PostgreSQL : Expertise, Formation et Support
C�dric Villemain wrote: > 2010/11/25 Bruce Momjian <bruce@momjian.us>: > > Document that a CHECKPOINT before taking a file system snapshot can > > reduce recovery time. > > I didn't follow that on -hackers, but : > > * checkpoint take place in the pg_start_backup process (before it > releases the hand, so before you can start snapshoting) > > * we used to issue a checkpoint *before* pg_start_backup to reduce > pg_start_backup duration in case you have wal_archiving turn off and > full_page_write is off, it reduces a bit the IO contention. (or even > if not I hate seing this pg_start_backup taking seconds/minutes to > finish) > > How the checkpoint before will reduce recovery time ? This is for using file system snapshots, not PITR or continuous archiving. The checkpoint reduces how much WAL has to be replayed. -- Bruce Momjian <bruce@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. +