追記(2014.02.19)：バグのようです。1.2.2から紛れ込んだ模様。開発者に連絡してもらったので、そのうち直るでしょう。
ドキュメントと違う挙動をしているように見える。
私の解釈が間違っているのか、使い方が間違っているのか？
ドキュメントの記述を抜粋。
- archive mode(アーカイブWAL): アーカイブWALのみのバックアップ
- incremental mode(増分バックアップ): 最新の検証済みバックアップの開始以降に変更のあったファイル・ページのみをバックアップします。
だけど、手元環境ではどちらもまったく同じで、アーカイブWALと変更ファイルの両方が保存される。
基本データ
実験環境。
pg_rman 1.2.7
因みに1.2.0も1.2.3も同じだった。
[postgres@localhost ~]$ env | grep BACKUP_PATH BACKUP_PATH=/home/postgres/backup_archives [postgres@localhost ~]$ cat $BACKUP_PATH/pg_rman.ini ARCLOG_PATH='/home/postgres/wal_archives'
postgresql 9.3.0
postgresql.conf
wal_level = hot_standby archive_mode = on archive_command = 'cp %p /home/postgres/wal_archives/%f' log_destination = 'stderr' logging_collector = on
archive modeの挙動
まずはarchiveモード。
[postgres@localhost ~]$ pg_rman backup --backup-mode=archive -D /usr/local/pgsql/data/ -d template1 [postgres@localhost ~]$ pg_rman validate [postgres@localhost ~]$ pg_rman show ============================================================================ Start Time Total Data WAL Log Backup Status ============================================================================ 2014-02-18 04:15:43 0m ---- ---- 33MB ---- 33MB OK 2014-02-18 04:00:13 0m 27MB ---- 83MB ---- 109MB OK
ドキュメントから期待するのは、archive log領域だけコピーしてくるだけども、データベースクラスタの(更新された)テーブルデータファイルもコピーしている。
[postgres@localhost ~]$ find backup_archives/20140218/041543/ backup_archives/20140218/041543/ backup_archives/20140218/041543/arclog backup_archives/20140218/041543/arclog/000000010000000000000007 backup_archives/20140218/041543/arclog/000000010000000000000006 backup_archives/20140218/041543/arclog/000000010000000000000007.00000028.backup backup_archives/20140218/041543/backup.ini backup_archives/20140218/041543/database backup_archives/20140218/041543/database/base backup_archives/20140218/041543/database/base/16384 backup_archives/20140218/041543/database/base/16384/16385 ＜＝＝ このファイルが何故、バックアップされるのか？ backup_archives/20140218/041543/database/base/12891 backup_archives/20140218/041543/database/base/12896 backup_archives/20140218/041543/database/base/1 backup_archives/20140218/041543/database/pg_twophase backup_archives/20140218/041543/database/pg_log backup_archives/20140218/041543/database/pg_notify backup_archives/20140218/041543/database/pg_snapshots backup_archives/20140218/041543/database/pg_tblspc backup_archives/20140218/041543/database/pg_tblspc/16388 backup_archives/20140218/041543/database/pg_tblspc/16388/PG_9.3_201306121 backup_archives/20140218/041543/database/pg_tblspc/16388/PG_9.3_201306121/16384 backup_archives/20140218/041543/database/pg_multixact backup_archives/20140218/041543/database/pg_multixact/members backup_archives/20140218/041543/database/pg_multixact/offsets backup_archives/20140218/041543/database/global backup_archives/20140218/041543/database/global/pg_control backup_archives/20140218/041543/database/pg_xlog backup_archives/20140218/041543/database/pg_serial backup_archives/20140218/041543/database/backup_label backup_archives/20140218/041543/database/pg_subtrans backup_archives/20140218/041543/database/pg_stat backup_archives/20140218/041543/database/pg_stat_tmp backup_archives/20140218/041543/database/pg_clog backup_archives/20140218/041543/database/pg_clog/0000 backup_archives/20140218/041543/mkdirs.sh backup_archives/20140218/041543/file_arclog.txt backup_archives/20140218/041543/srvlog backup_archives/20140218/041543/file_database.txt
incremental mode の挙動
次にincrementalモード。
[postgres@localhost ~]$ pg_rman backup --backup-mode=incremental -D /usr/local/pgsql/data/ -d template1 INFO: database backup start NOTICE: pg_stop_backup complete, all required WAL segments have been archived [postgres@localhost ~]$ pg_rman validate INFO: validate: 2014-02-18 04:27:39 backup and archive log files by CRC [postgres@localhost ~]$ pg_rman show ============================================================================ Start Time Total Data WAL Log Backup Status ============================================================================ 2014-02-18 04:27:39 0m ---- 24kB 33MB ---- 33MB OK 2014-02-18 04:15:43 0m ---- ---- 33MB ---- 33MB OK 2014-02-18 04:00:13 0m 27MB ---- 83MB ---- 109MB OK
こっちは、変更のあったテーブルと、archive log領域がコピーされている。
つまり、archiveモードとincrementalモードは同じ挙動を示す！？。
[postgres@localhost ~]$ find backup_archives/20140218/042739/ backup_archives/20140218/042739/ backup_archives/20140218/042739/arclog backup_archives/20140218/042739/arclog/000000010000000000000009 backup_archives/20140218/042739/arclog/000000010000000000000008 backup_archives/20140218/042739/arclog/000000010000000000000009.00000028.backup backup_archives/20140218/042739/backup.ini backup_archives/20140218/042739/database backup_archives/20140218/042739/database/base backup_archives/20140218/042739/database/base/16384 backup_archives/20140218/042739/database/base/16384/16385 backup_archives/20140218/042739/database/base/12891 backup_archives/20140218/042739/database/base/12896 backup_archives/20140218/042739/database/base/1 backup_archives/20140218/042739/database/pg_twophase backup_archives/20140218/042739/database/pg_log backup_archives/20140218/042739/database/pg_notify backup_archives/20140218/042739/database/pg_snapshots backup_archives/20140218/042739/database/pg_tblspc backup_archives/20140218/042739/database/pg_tblspc/16388 backup_archives/20140218/042739/database/pg_tblspc/16388/PG_9.3_201306121 backup_archives/20140218/042739/database/pg_tblspc/16388/PG_9.3_201306121/16384 backup_archives/20140218/042739/database/pg_multixact backup_archives/20140218/042739/database/pg_multixact/members backup_archives/20140218/042739/database/pg_multixact/offsets backup_archives/20140218/042739/database/global backup_archives/20140218/042739/database/global/pg_control backup_archives/20140218/042739/database/pg_xlog backup_archives/20140218/042739/database/pg_serial backup_archives/20140218/042739/database/backup_label backup_archives/20140218/042739/database/pg_subtrans backup_archives/20140218/042739/database/pg_stat backup_archives/20140218/042739/database/pg_stat_tmp backup_archives/20140218/042739/database/pg_clog backup_archives/20140218/042739/database/pg_clog/0000 backup_archives/20140218/042739/mkdirs.sh backup_archives/20140218/042739/file_arclog.txt backup_archives/20140218/042739/srvlog backup_archives/20140218/042739/file_database.txt
ソース
backup.cをザックリ見ると、
if (current.backup_mode < BACKUP_MODE_FULL) {
とか
if (current.backup_mode == BACKUP_MODE_FULL)
{
delete_online_wal_backup();
delete_arclog_link();
}
などなど、fullバックアップの記述はあるけども、incrementとarchiveの違いを生み出すはずの条件式が見当たらない。もっともgrepでcurrent.backup_modeを調べた限りだが。
archiveとincrementの違いがでるのは唯一、showコマンドだが、それは単にオプションとして保存しているから表示が異なるだけ。実際にバックアップ処理を行っているbackup.cの中では扱いに違いがない。
上の実験結果をもとにソースを眺めたから、なんらかの先入観があるのかもしれないが、どうもおかしい。
この挙動は、手元で実験する限りver1.2.0ver1.2.3から。それ以前のバージョンはコンパイルできないので試せない。
さて、どうなっているんでしょう？
