On Thu, May 27, 2010 at 11:13 PM, Robert Haas <robertmh...@gmail.com> wrote: >> I guess this happens because the frequency of checkpoint on the standby is >> too lower than that on the master. In the master, checkpoint occurs for every >> consumption of three segments because of "checkpoint_segments = 3". On the >> other hand, in the standby, only checkpoint_timeout has effect, so checkpoint >> occurs for every 30 minutes because of "checkpoint_timeout = 30min". >> >> The walreceiver should signal the bgwriter to start checkpoint if it has >> received more than checkpoint_segments WAL files, like normal processing? > > Is this also an issue when using log shipping, or just with SR?
When using log shipping, checkpoint_segments always doesn't trigger a checkpoint. So recovery after the standby crashes might take unexpectedly long since redo starting point might be old. But in file-based log shipping, since WAL files don't accumulate in pg_xlog directory on the standby, even if the frequency of checkpoint is very low, pg_xlog will not be filled with many WAL files. That accumulation occurs only when using SR. If we should avoid low frequency of checkpoint itself rather than accumulation of WAL files, the bgwriter instead of the walreceiver should check if we've consumed too much WAL, I think. Thought? Regards, -- Fujii Masao NIPPON TELEGRAPH AND TELEPHONE CORPORATION NTT Open Source Software Center -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
