Thread: Question about PITR backup
| Dear admin, I have a question about PITR backup in a single server, the method is make a base backup, and backup the WAL archive log(eg, every day at 11:30 pm). But if the OS' harddisk is broken(eg,14:00 pm),the system can't start, we have to recover the database on a another server using the base backup and the WAL backup,so in this case suppose that we only can restore the database to yesterday's 11:30 pm state, am I right? How can we recover the database to 14:00 pm? We are missing the newest pg_xlog. I want to backup the pg_xlog folder every minute by crontab but my concern is that the data inconsistent, because the lastest log in pg_xlog is being updated all the time, am I right? Any suggestions? Very appreciated your answer. Thanks, Song |
sgm <sgm277@yahoo.com.cn> wrote: > I have a question about PITR backup in a single server, the method > is make a base backup, and backup the WAL archive log(eg, every > day at 11:30 pm). But if the OS' harddisk is broken(eg,14:00 > pm),the system can't start, we have to recover the database on a > another server using the base backup and the WAL backup,so in this > case suppose that we only can restore the database to yesterday's > 11:30 pm state, am I right? You can't recover to a point past your last available WAL record. > I want to backup the pg_xlog folder every minute by crontab but my > concern is that the data inconsistent, because the lastest log in > pg_xlog is being updated all the time, am I right? Any > suggestions? Use streaming replication? Or at the very least, set a short archive_timeout value and copy from the archive target location frequently. -Kevin
Am 08.06.2012 05:43, schrieb sgm:
Yes, the wal segments are updated constantly. You'll have a consistent state in your data files up to the time when the last checkpoint happened. Should a crash occur the server will replay the log segments in the WAL files starting from the one that was marked during the last checkpoint recorded.
So,provided all the WAL files generated by the server after the last checkpoint are available, it will always be able to bring the data files to a consistent state. Those WAL files are always kept in the pg_xlog directory.
Though I'm also in favor of leveraging a streaming replication configuration as it's more reliable and the window for data loss is very small.
Dear admin, I have a question about PITR backup in a single server, the method is make a base backup, and backup the WAL archive log(eg, every day at 11:30 pm). But if the OS' harddisk is broken(eg,14:00 pm),the system can't start, we have to recover the database on a another server using the base backup and the WAL backup,so in this case suppose that we only can restore the database to yesterday's 11:30 pm state, am I right?How can we recover the database to 14:00 pm? We are missing the newest pg_xlog.I want to backup the pg_xlog folder every minute by crontab but my concern is that the data inconsistent, because the lastest log in pg_xlog is being updated all the time, am I right? Any suggestions?
Yes, the wal segments are updated constantly. You'll have a consistent state in your data files up to the time when the last checkpoint happened. Should a crash occur the server will replay the log segments in the WAL files starting from the one that was marked during the last checkpoint recorded.
So,provided all the WAL files generated by the server after the last checkpoint are available, it will always be able to bring the data files to a consistent state. Those WAL files are always kept in the pg_xlog directory.
Though I'm also in favor of leveraging a streaming replication configuration as it's more reliable and the window for data loss is very small.