Re: Snapshot backups
| От | Amit Langote |
|---|---|
| Тема | Re: Snapshot backups |
| Дата | |
| Msg-id | CA+HiwqFhukXr-GyNZiUgPJP=5Fobsa2UTgeC=p4=sA8r4hW+eA@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Snapshot backups (James Sewell <james.sewell@lisasoft.com>) |
| Ответы |
Re: Snapshot backups
|
| Список | pgsql-general |
On Mon, Jul 29, 2013 at 3:32 PM, James Sewell <james.sewell@lisasoft.com> wrote:
-- Hey all,I understand that I have already been given an answer here, but I am still curious as to why this is the case (perhaps I should ask this on the hackers list though, if so let me know).More importantly I'd like to understand why I would need to use the start/stop backup commands to ensure a valid backup when using filesystem snapshots (assuming I get the order correct)- worst case scenario wouldn't it be the same as a crash and cause an automatic roll-forward?
pg_start_backup('backup_label') and pg_stop_backup(), if I understand it correctly, write to the 'backup_label' file the information necessary to recover "consistently" from that backup. For example, backup_label file contains the checkpoint location and its REDO location (identified as "START WAL LOCATION:" field in the backup_label file.) While you are reading the code, you can read the comment above the function read_backup_label() in src/backend/access/transam/xlog.c
Amit Langote
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