数据库的PITR是一般数据库都必须满足的技术。其原理是依据之前的物理备份文件加上wal的预写日志模式备份做的恢复。该技术支持8.*及以上版本。下面主要概述PITR的准备和恢复过程。 测试环境 ~~~ OS 环境：CentOS 6.2 数据库 ：PostgreSQL 9.1.3 pg_home=/home/postgres/ pg_data=/database/pgdata/ ~~~ 一、前期工作既要恢复，肯定是需要一个备份基础的，否则再怎么的巧妇也难为无米之炊。  1.修改数据库参数，修改postgresql.conf： ~~~ archive_mode = on archive_timeout = 300 --单位是秒，此处以5分钟为限强制归档，仅作测试 archive_command = 'cp -i %p /home/postgres/archive/%f' wal_level = archive ~~~ 修改完重启下reload,DB  2.基于文件级别的持续备份，  a.基础备份  postgres=# select pg_start_backup('backup_2012_05_20_14:22:10');  b.打包备份pg_data  # cd /database  # tar -cvzf pgdata.tar ./pgdata  c.结束基础备份并切换归档 ~~~ postgres=# select pg_stop_backup(); postgres=# select pg_switch_xlog(); pg_switch_xlog ---------------- 0/C000020 (1 row) postgres=# select pg_current_xlog_location(); pg_current_xlog_location -------------------------- 0/C000020 (1 row) postgres=# create table test_1(id int,name varchar(50)); postgres=# insert into test_1 values (1,'kenyon'); INSERT 0 1 ~~~ 此时在pg_data路径下会产生一个label,可以查看内容有checkpoint时间,基础备份的开始和结束时间，以及标签名称等。因为之前已经设置了archive的三个参数，可以在archive的备份路径pg_home/archive下看到归档的文件会定时传过来。  二、恢复过程 停数据库  # pg_stop  假定数据库的崩溃场景，将pgdata数据删除  # rm -rf /database/pgdata  恢复之前备份的tar文件  # tar xvf pgdata.tar  删除pg_xlog文件夹并重建  # rm -rf pg_xlog # mkdir -p pg_xlog/archive_status  拷贝recovery.conf文件并修改  # cp $PG_HOME/recovery.conf.sample /database/pgdata/  # vi /database/pgdata/recovery.conf  --新增内容，指定恢复文件和路径，%f,%p见上面说明  restore_command = 'cp /home/postgres/archive/%f "%p"'  启动数据库 ~~~ # pg_start [postgres@localhost archive]$ psql spsql (9.1.3) Type "help" for help. postgres=# select * from test_1; id | name ----+-------- 1 | kenyon (1 rows) ~~~ --恢复成功，会恢复到之前接收到的最后一个归档文件。另外recovery.conf会改名变成recovery.done  日志内容: ~~~ LOG: shutting down LOG: database system is shut down LOG: database system was interrupted; last known up at 2012-05-20 22:23:15 CST LOG: starting archive recovery LOG: restored log file "000000010000000000000002" from archive LOG: redo starts at 0/8000078 LOG: consistent recovery state reached at 0/C000000 LOG: restored log file "000000010000000000000003" from archive LOG: restored log file "000000010000000000000004" from archive LOG: restored log file "000000010000000000000005" from archive LOG: restored log file "000000010000000000000006" from archive LOG: restored log file "000000010000000000000007" from archive cp: cannot stat `/home/postgres/archive/000000010000000000000008': No such file or directory LOG: could not open file "pg_xlog/000000010000000000000008" (log file 0, segment 8): No such file or directory LOG: redo done at 0/1C000078 LOG: last completed transaction was at log time 2012-05-20 23:01:22.960591+08 LOG: restored log file "000000010000000000000007" from archive cp: cannot stat `/home/postgres/archive/00000002.history': No such file or directory LOG: selected new timeline ID: 2 cp: cannot stat `/home/postgres/archive/00000001.history': No such file or directory LOG: archive recovery complete LOG: database system is ready to accept connections LOG: autovacuum launcher started ~~~ PS:若要恢复到指定时间，还需要再recovery.conf中设置recovrey_target_time,recovery_target_timeline等参数 总结：pitr技术对于7*24小时支撑是至关重要的，但是如果数据库非常小，增大pg_dump备份的频率可能更方便，但对于大数据库就需要了。