Best OS for Xen Dom0 – have had problems with CentOS and OpenSUSE for Xen

Your questions is a little unclear as to what kind of stats you are hoping to collect from the dom0, but I think what you are looking for is an understanding of how your existing hardware resources are allocated.

We're having great success using libvirt's Python bindings to get this information. Here's a Python script snippet that illustrates the idea:

#!/usr/bin/env python

import sys
import libvirt

def main(options,args):
    hypervisors = sys.argv[1:]

    print "%16s%18s%18s%18s" % ("dom0 IP", "Free Memory (MB)", "Disk Used (GB)", "Disk Free (GB)")
    for ip in hypervisors:
        # this assumes "remote" connection to libvirtd using TCP
        url = "xen+tcp://%s" % (ip)

        conn = libvirt.open(url)
        # you may want to do more error handling here
        if conn == None:
            continue

        mem = conn.getFreeMemory() / 1048576 #convert bytes -> megabytes
        pool = conn.storagePoolLookupByName('vol0')
        # a refresh() is necessary because libvirtd's internal information isn't
        # always in sync with the host.
        pool.refresh(0)
        disk_info = pool.info()
        disk_used = disk_info[2] / 1073741824 #convert bytes -> gigabytes
        disk_free = disk_info[3] / 1073741824 #convert bytes -> gigabytes
        print "%16s%18d%18s%18d" % (ip, mem, disk_used, disk_free)

if __name__ == '__main__':
    sys.exit(main(options,args))

What is the result of 'uname -a' on the host machine? Do you have a Xen enabled kernel loaded (on the host)? It should be something like:

2.6.18-92.1.10.el5xen

With xen at the end. If you are booting with a normal kernel, install the xen package with 'yum install kernel-xen' and boot with this new kernel.