how to do multiple installations of membase on a single machine

I need to use a few memcached buckets for caching some small data( less than 64 MB) and a few to cache larger datasets. For this I decided create a cluster with just one node to cache small datasets and another cluster with 3-4 machines for larger datasets. This will make a better use of my RAM. Now in case I need to have the single node membase to run on one of the machines that hosts a membase node of 4 node membase cluster, I will need to make sure that I can run two instances of membase on one machine. I am unable to do so now with following error :
=PROGRESS REPORT==== 6-Sep-2011::11:15:44 ===
supervisor: {local,ns_server_cluster_sup}
started: [{pid,<0.60.0>},
{name,ns_log_mf_h},
{mfargs,{ns_log_mf_h,start_link,[]}},
{restart_type,permanent},
{shutdown,1000},
{child_type,worker}]
{[47,111,112,116,47,109,101,109,98,97,115,101,47,118,97,114,47,108,105,98,47,109,101,109,98,97,115,101,47,
108,111,103,115],10485760,20,#Fun}{"init terminating in do_boot",{{badmatch,{error,{shutdown,{ns_server,start,[normal,[]]}}}},[{init,start_it,1},{init,start_em,1}]}}
/opt/membase/lib/erlang/lib/os_mon-2.2.5/priv/bin/memsup: Erlang has closed.

I can't find a config file that can be changed to rename ns servers or whatever that is needed changing. Can you please tell me how I can do multiple membase installs.

thanks!