When to use multiple vSphere Distributed Switches

[StageCoach20111]

I have a number of port groups that will reside on distributed switches.   I have a number of clusters.  Some clusters are dedicated to only containing certain kinds of VMs which are all on the same port groups.  For example my SQL server vms are all on one cluster.  They are also all on the same vlans and port groups.  The other clusters don't have vms that need to be on those port groups.

For example, when I have a separate SQL cluster that needs access to only an exclusive set of port groups, and those port groups aren't needed anywhere else, is that a good enough reason to create a separate distributed switch that has just those port groups - and just add that cluster to that distributed switch?

If I keep doing that for every cluster I build that has unique vms with unique vlans, eventually I would have a lot of distributed switches.  When does having too may distributed switches become a problem?

Thanks for your input. 

[StageCoach20111]

Anyone have any ideas?

[chriswahl]

I typically split out into a new VDS when security (compliance, air gaps), management (who is making changes, risk of change, prod vs non-prod, etc), or underlying physical configuration (such as mixing 2 NIC hosts with 8 NIC hosts) becomes an issue. For each decision point, weigh in on these three items and, if you still fee comfortable, re-use your existing VDS. If not, create a new one.