add HA pair to existing cluster or build a separated cluster

[FelixZhou]

we have a two node AFF400 cluster, plan to expand it with another two nodes of AFF800. we know we can expand the existing cluster to have four nodes with two HA pairs or optionally to have two clusters, one for AFF400, another one for AFF800. 

Since the AFF800 will be used dedicatedly for Exchange servers only. is there any suggestion which one is better for us?

for a single cluster, we know it is a better idea if we have data moving around between two pairs, but if any cluster maintenance, will all four nodes be affected?

thanks in advance.

[SpindleNinja · Accepted solution]

Clustering them all together does give a single point for mgmt and flexibility down the line.    I have customers were it's all in one cluster and others were everything is seperate.  Pros and cons to each honestly.  

As far as "but if any cluster maintenance, will all four nodes be affected"  The whole cluster will need to be updated,  but outside of that.. there isn't anything I can think of.    

The cluster switches are an additional maintenance point too.