How Do You Determine The Active Node Inside A Stored Proc For An Active/passive 2-node Cluster?

I invoke xp_cmdshell proc from inside a stored procedure on a 2-node active/passive SQL 2005 SP2 Standard cluster. Depending on which server the xp_cmdshell gets executed on I need to pass different arguments in the shell command. I thought I could use host_name() function to get the runtime process server, however, I am finding that it's not behaving correctly. In one example I know my active node is server2, but the host_name() function is returning server1. The only thing that I could possible explain this is that the MSDTC cluster group is not always on the same active node as the SQL server group and in the case I am talking about the cluster groups are in this mode (differnet nodes). Does the xp_cmdshell get executed by the SQL active node or the MDTC active node? And what is the best way to find out which server is going to run my xp_cmdshell?

Thanks.

Edit:

Perhaps another by product of this is that if I run select host_name() from the Studio Management query window i get different results depending on which server I am running the Studio Management on. On server1 I get server1 and on server 2 I get server 2, all the while server2 is the active node. I need a different function that will always let me determine the correct server that'll be running the xp_cmdshell...

Edit 2: I guess I could determine the running host inside the command shell itself, but I am curious to see if i can do it (cleaner) from SQL.