Running multiple instances of the server is possible, be it for debugging purposes or just for the personal experience.
And my personal experience on a 2-Core Intel CPU with 2,67 GHz BIOS year 2008 is very pleasing: 8 instances were running, without much CPU-usage as shown by the xosview application.

There are some problems when running multiple instances of the server; mainly the LOCALDIR and LIBDIR (DATADIR) handling may confuse the (other) servers, if these are shared.
One solution would be to pass positional parameters to the server at start up time, the other solution would be to use environment variables .