Hot swap RAM?

I don't believe any Dell servers have hotswap ram. Some have hotswap PCI-X slots (which I would personally not risk (if your setup is that crucial, just run a cluster so you can fail over to the other node while you perform service on the server that needs to have a card replaced)), but not hot swap ram.

The way I understand it, the failover ram is more like a hotspare dimm; it does nothing till the systemboard sees a dimm is faulty, at which time it switches to using the hotspare dimm so you can plan for the downtime to replace the faulty dimm and be less likely to run into an OS lockup due to faulty memory.

Alright, thanks. =)

The PE 6850 will support Hot add and Hot Replace. The memory need to be in a memory RAID or mirroring configuration in order for it to work. I think that is about the only system that supports it though and you can only have one memory riser out at a time.