I would not have an important live server relying on a single FusionIO card.

RAID1 is the safe route for production.

Got several of these cards in various configurations - example 2x640 in RAID0 create a pretty fast 1.2TB drive:-D, but if you cannot afford service disruption it's best to have them as a single 640GB in software RAID1. Yes it sucks that you 'waste' a card and the throughput is a bit lower, but you are doing the right thing:cool:

Also remember to allow for free RAM just to handle the FusionIO cards, they need RAM space to 'breath' (used to be ~2GB RAM for every 80GB of SSD, YMMV)

So there you have it, you cannot skimp on RAM after all:-)