Keep in mind that your upper scaling limit is determined by the hybrid 3655 PAN/MNT nodes. You can support 25k active endpoints in this case, even though the 3615's have a combined capacity of 40k.
Changing the hardware config of a SNS appliance is not supported, but there is one common change that we make in the field. It is very common for 3515/3615 purchases to include a second c220 power supply. I've never had an issue with this, but from an RMA perspective, if you ship the box back with your second PSU, you will get a new box with only one PSU. You need to remove the PSU before you ship an appliance back during a RMA.
Adding RAID to the SNS 3615 is not a field supported change, but there is nothing stopping you from adding disks. At the end of the day, a SNS is still a C220M5 server. If you added a Cisco 12G SAS Modular RAID Controller like found in the 3655/3695, and three more 10k 600 GB SAS disks, it would certainly work. If one was to do this, then matching the same hardware as the 3655/3695 would be ideal since the OS would be guaranteed to work from a driver level.
Big warning here, it has not been tested, TAC doesn't have to support it if they don't want, and you may have to remove all your hardware if it is called in to question. I wouldn't recommend going down that path of adding RAID to a 3615.
