On Tue, Oct 25, 2011 at 7:37 PM, Magnus Hagander <mag...@hagander.net> wrote: > On Mon, Oct 24, 2011 at 14:40, Magnus Hagander <mag...@hagander.net> wrote: >> On Mon, Oct 24, 2011 at 13:46, Heikki Linnakangas >> <heikki.linnakan...@enterprisedb.com> wrote: >>> How does this interact with synchronous replication? If a base backup that >>> streams WAL is in progress, and you have synchronous_standby_names set to >>> '*', I believe the in-progress backup will count as a standby for that >>> purpose. That might give a false sense of security. >> >> Ah yes. Did not think of that. Yes, it will have this problem. > > Actually, thinking more, per other mail, it won't. Because it will > never report that the data is synced to disk, so it will not be > considered for sync standby.
Now, new replication mode (synchronous_commit = write) is supported. In this mode, the in-progress backup will be considered as sync standby because its periodic status report includes the valid write position. We should change the report so that it includes only invalid positions. Patch attached. While I agree that the backup should not behave as sync standby, ISTM that pg_receivexlog should, which is very useful. If pg_receivexlog does so, we can write WAL synchronously in both local and remote, which would increase the durability of the system. Thus, to allow pg_receivexlog to behave as sync standby, we should change it so that its status report includes the write and flush positions? Regards, -- Fujii Masao NIPPON TELEGRAPH AND TELEPHONE CORPORATION NTT Open Source Software Center
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