Обсуждение: Backup's from standby
What is the basic reason for restricting backup at standby server(pg_start_backup)? We are doing the following steps to take backup from standby which(backups) might be used for standalone startups. 1.Create file system snapshot(LVM) 2.take the back up of data directory including wal files 3.Drop the file system snapshot Will there be(foresee) any issues while using these backups? -Senthil -- View this message in context: http://postgresql.1045698.n5.nabble.com/Backup-s-from-standby-tp4688344p4688344.html Sent from the PostgreSQL - hackers mailing list archive at Nabble.com.
On Thu, Aug 11, 2011 at 1:02 AM, senthilnathan <senthilnathan.t@gmail.com> wrote: > What is the basic reason for restricting backup at standby > server(pg_start_backup)? It performs a checkpoint. > We are doing the following steps to take backup from standby which(backups) > might be used for standalone startups. > > 1.Create file system snapshot(LVM) > 2.take the back up of data directory including wal files > 3.Drop the file system snapshot > > Will there be(foresee) any issues while using these backups? Assuming that step #2 is backing up an instantaneous snapshot, rather than the live data directory, I think that will work. Upon starting up the server, it will enter recovery, but the WAL present in the data directory at the time of the snapshot should be sufficient to reach the minimum recovery point. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
Thanks for your reply. What will happen if you issue *checkpoint* at STANDBY. I presume that it will flush the data to the disk. Will there be any conflict with the master WAL.(like checkpoint location...) Senthil -- View this message in context: http://postgresql.1045698.n5.nabble.com/Backup-s-from-standby-tp4688344p4703469.html Sent from the PostgreSQL - hackers mailing list archive at Nabble.com.
On Tue, Aug 16, 2011 at 2:34 AM, senthilnathan <senthilnathan.t@gmail.com> wrote: > Thanks for your reply. > > What will happen if you issue *checkpoint* at STANDBY. I presume that it > will flush the data to the disk. It will perform a restartpoint. http://www.postgresql.org/docs/9.0/static/wal-configuration.html -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
On Tue, Aug 16, 2011 at 7:34 AM, senthilnathan <senthilnathan.t@gmail.com> wrote: > Thanks for your reply. > > What will happen if you issue *checkpoint* at STANDBY. I presume that it > will flush the data to the disk. Yes. On the standby that is known as a restartpoint. > Will there be any conflict with the master WAL.(like checkpoint location...) No, there is no effect on the master. The restartpoint happens as a background process on the standby, so replay will continue while we restart. -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
Thanks for your reply., @ Robert., What issue we may face if you take a backups(includes data dir + wal files) at standby without LVM snapshot? -Senthil -- View this message in context: http://postgresql.1045698.n5.nabble.com/Backup-s-from-standby-tp4688344p4706899.html Sent from the PostgreSQL - hackers mailing list archive at Nabble.com.
On Wed, Aug 17, 2011 at 1:39 AM, senthilnathan <senthilnathan.t@gmail.com> wrote: > Thanks for your reply., > > @ Robert., > > What issue we may face if you take a backups(includes data dir + wal files) > at standby without LVM snapshot? The backup might be corrupted in arbitrary ways. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
> > What issue we may face if you take a backups(includes data dir + wal files)
> > at standby without LVM snapshot?
>
> The backup might be corrupted in arbitrary ways.
>
> > at standby without LVM snapshot?
>
> The backup might be corrupted in arbitrary ways.
>
-- Valentine Gogichashvili
On Fri, Aug 19, 2011 at 9:38 AM, Valentine Gogichashvili <valgog@gmail.com> wrote: >> > What issue we may face if you take a backups(includes data dir + wal >> > files) >> > at standby without LVM snapshot? >> >> The backup might be corrupted in arbitrary ways. > > And what will happen, if one issues a pg_start_backup() on the master, then > takes a file-backup on slave, and issues pg_stop_backup() on master again? > As far as I remember this approach was working for me, considering, that all > needed WAL files are transferred to the newly created DB copy as well. Well, I think you would need to verify a few more things: - The pg_start_backup() will need to have been replayed on the standby before you start the file copy. - You will need all the WAL segments beginning at the position where pg_start_backup() was executed on the master and ending after pg_stop_backup() was executed on the master. Assuming you do that, it seems like it ought to work, although I have not tested it and am not at all sure I'm not missing something. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company