slapd is the OpenLDAP daemon. You should look into your directory bindings. Is your MDC also your OD master? If so, you definitely need more RAM. Heck, you need more RAM regardless. 3GB isn't enough for Xsan, let alone running other processes as well. You should have at least 2GB for the OS, 2GB more for each Xsan volume you run, and more still if you host other services. You should install at least 4GB for the OS and 2GB for each Xsan volume.
Best,
Andy