Sorry I haven't been handling the system administration (I just 'code' the pages), and truthfully we tried it for about 3 weeks - and now are switching back. But certainly that isn't enough time to really root cause determine anything definitive. The behavior we found is that the python process running as the "Zeo Client" eventually takes up a large amount of resident memory (1.5 Gig or so), load average gets high (1.5 or so), and the end users start experiencing a very 'slow' experience. Even when traffic is removed from the box - you still get a large response time (>10s). This is Linux kernel 2.6.18-8.el5xen. This is actually the issue we are having on FreeBSD (version 5.3) but the resident memory and load remains 1/2 of the above - and when traffic is removed from the box - you can then get a reasonable response (< 10s). I know it's not very scientific. We have a 'support agreement' with RH, so we are heading that way. But because the existing ZEO Server runs FreeBSD - and we are having performance issues, we figured to put everything back to the same OS while we try to figure out the performance part. When we investigate migrating from FreeBSD to RH for "real" - I'll certainly update this list if any of our findings would be of interest to anyone else.