[Linux-cluster] Xen , Out of memory and dom0-min-mem, dom0_mem

[FM]

Hello
2 of 3 of my xen nodes ( dom0) died tonight because of out of memory error.
These servers are only running Xen and cluster suite packages.
I googled the error and everything point out to dom0-min-mem and grub 
dom0_mem options

dom0-min-mem : I left it by default : (dom0-min-mem 256)

I read about on the internet but still do not understand this parameter 
and if if should be =0 on servers

any advice ?

tx !

here are some info about one server  :

[root at cluster01-node1 xen]# virsh dominfo 0
Id:             0
Name:           Domain-0
UUID:           00000000-0000-0000-0000-000000000000
OS Type:        linux
State:          running
CPU(s):         8
CPU time:       182.8s
Max memory:     no limit
Used memory:    33554544 kB



host                   : cluster01-node1.cluster.lexum.pri
release                : 2.6.18-128.1.10.el5xen
version                : #1 SMP Thu May 7 11:07:18 EDT 2009
machine                : x86_64
nr_cpus                : 8
nr_nodes               : 1
sockets_per_node       : 2
cores_per_socket       : 4
threads_per_core       : 1
cpu_mhz                : 2833
hw_caps                : 
bfebfbff:20000800:00000000:00000140:040ce3bd:00000000:00000001
total_memory           : 36861
free_memory            : 963
node_to_cpu            : node0:0-7
xen_major              : 3
xen_minor              : 1
xen_extra              : .2-128.1.10.el5
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 
hvm-3.0-x86_32p hvm-3.0-x86_64
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : unavailable
cc_compiler            : gcc version 4.1.2 20080704 (Red Hat 4.1.2-44)
cc_compile_by          : mockbuild
cc_compile_domain      : centos.org
cc_compile_date        : Thu May  7 10:28:47 EDT 2009
xend_config_format     : 2