Seeing as Nic brought up the subject of LBs, I thought I would chime in with the BalanceNG product which is not currently certified for Exchange or any other MS products. However seeing as it’s probably one of the best LBs I’ve ever used ( and that includes Alteon and Zeus ZXTM ), it merits a mention.
The first aspect of BalanceNG is its capacity for packet redirection on even low hardware platforms. It’s quite easy to saturate a 100Mbps link using entry level CPUs like Via C3 and Atoms. In fact I’ve extrapolated that you can exceed 25MB’s on a GbE link using the same hardware.
Next is the feature set which includes up to 1024 virtual servers per license, easy built-in active-passive clustering with stateful fail-over, port translation and grouping, full IPv6 support, balanced or backup targets, Direct Server Return and many more.
And lastly is the price: Eu1200 per node ( you typically want 2 nodes for clustering fail-over ). This is somewhat lower than many hardware solutions, even after you factor in some decent hardware to run this on. Inlab also have some hardware OEMs that provide pre-installed systems with nice Web Interfaces for management.
All in all, a very nice product at a very reasonable price.