I have found that the situations you really need clustering are few and far between in the world of web apps. We had over 20M users and we're running fine on o

I have found that the situations you really need clustering are few and far between in the world of web apps. We had over 20M users and we're running fine on one 2U database server. It had 6 disks (RAID 5, with two hot spares) and 16GB of memory. The indexes all fit in memory. The acquiring company of our business immediately decided they wanted more hardware for clustering, and set up Slony. I was semi-involved in it, and I witnessed no problems. On a bigger scale, I understand that skype uses pgsql and obviously does clustering: https://developer.skype.com/SkypeGarage/DbProjects/SkypePostgresqlWhitepaper https://developer.skype.com/SkypeGarage/DbProjects/SkypePost... Also check out http://highscalability.com/postgresql-high-availability-websites http://highscalability.com/postgresql-high-availability-webs... and http://highscalability.com/skype-plans-postgresql-scale-1-billion-users http://highscalability.com/skype-plans-postgresql-scale-1-bi...