We have a customer that is currently supporting 9 sites with Cisco WAAS (4.0.11) WAEs. A single 612/4GB is serving as the Core with 9 512/2GB units serving the remote sites. Most remote sites are T1 the home office is 2x15Mbps. Currently we have 3500 active connections on the core device. It is able to support 6000. We plan on adding additional sites this year pushing the active connections passed the supported limit. We are considering adding an additional WAE to support the load.
What is the recommended best practice for adding WAE to a service group. Do we need to add same size/spec WAEs to the group? I didn't see anything in the WCCP draft that notes load balancing based on the TCP load of the cache.
Best practices would be to add another box of the same hardware. If you are concerned with failover, then your should size the core cluster by N+1 to allow for connections to be serviced on a box failure.
WCCP Services 61 and 62 load balances by source (61) and destination (62) IP addresses, nothing to do with TCP load. If a box goes into overload, then the traffic isn't sent to the other WAE. You can swap the services applied to the LAN and WAN interfaces to reverse load balancing, however I would recommend that in the DC you use 61 on the WAN and 62 on the LAN to load balance by your client IP addresses (which should have higher IP variances then your DC).
Hope that helps,