>> [ scratches head... ] It should certainly not have taken very long to >> replay 10 WAL segments worth of data. I surmise that the problems >> you were having before the shutdown were worse than you thought, ie >> checkpoints were failing to complete, probably due to a persistent >> I/O error, so that there was a whole lot more than normal to replay >> after the last successful checkpoint. Is there any evidence of such >> distress in the postmaster log?
> We had very slow application performance and many hanging threads as per > pgadmin -> server status > Also logs had the following which also indicating probably high I/O (as per > google search results)
> 2015-07-30 10:10:21 IST WARNING: pgstat wait timeout > 2015-07-30 10:12:21 IST WARNING: pgstat wait timeout
Well, those might mean problems with the stats collector subprocess, but that's pretty noncritical; it would certainly not have prevented checkpoints from completing. No other unexplained log entries?
None. I have default log configuration as given by Ubuntu as default. Probably I would need to increase them to get some more detailed level. I will do some reading on them.
As of now, logging_collector and other log related are commented out, so whatever is default is functioning and logging to postgresql-9.1-main.log
If you have some suggestions, please let me know.
One area of concern, I am realising now which might have contributed to this is below.
I am using postgres as backend db of a java based application over tomcat. JVM is allocated 2048 MB memory heap size from tomcat. But shared_buffers in postgres was at the default of 32m. I increased them to 144 M and increased shmmax to 320 M. This machine has 8 GB RAM and used as Database and Tomcat/application server. I can allocate more memory, but my application side colleagues like to know why we keep high and how to figure out instead of blindly allocating a high memory.
I am not even sure how to figure out what should be my buffers.
I now kept effective_cache_size = 256MB max_connections = 100 work_mem = 10MB
and all others are default provided by postgres 9.1 in Ubuntu 12.04
