Question about namenode HA

[谢良]

Hi Todd and other HA experts,

I've two question:

1) why the zkfc is a seperate process, i mean, what's the primary design 
consideration that we didn't integrate zkfc features into namenode self ?

2) If i deploy CDH4.1(included QJM feature),  since QJM can do fencing writer,  
so can i just config like this safely ?
        <name>dfs.ha.fencing.methods</name>
        <value>shell(/bin/true)</value>

Thanks,
Liang