I am migrating a Postgres 8.4 installation on a dedicated server to Postgres 9.2 running on a Virtual Machine. A sample query that run in 10 minutes on the 8.4 installation take 40 minutes on the 9.2 installation.
Current Server, Postgres 8.4
· 6-core, 3GHz AMD system
· 12GB of RAM
· 4 SATA drive RAID-1 storage
· Mandriva OS
· SQL encoding and ‘C’ collation
Virtual Machine, Postgres 9.2 ( two different systems)
· 4-core, 3Ghz Intel system
· 12GB or RAM
· SAS storage on one, and 4-SATA drive RAID-10 system on second
· CentOS 6.3 OS
· UTF-8 encoding, and I have tried both ‘C’ and en_US collation
The first VM is at a local Data Center and the second in on a dedicated server in my office. Both give similar results.
The data, indexes and constraints have all been successfully migrated to the new system.
I have tuned the VM systems using pgtune with no significant before and after difference.
The ‘explain’ output for the query is very different between the two systems.
It seems like I am missing some simple step for there to be such a huge performance difference.
Any suggestions on what else to text/check would be very much appreciated.
Tom
