I got a FW800 to 400 Cable off ebay and have not had any trouble with it. If the cheap one is not working out for you then Dick Smith sell a Belkin Brand one but it costs you $40 - in my opinion not worth it.
In my testing I found that USB2 was overall faster than Firewire 400. The main difference between the two is that USB is handled mainly in the software driver (so uses your computers CPU) while Firewire is handled by a chip on your motherboard.
In general people have said that USB2 at 480Mbits gives higher burst rates while Firewire 400 at 400Mbits gives consistent speeds - so firewire 400 is better overall. My experience is that with modern dual-core CPUs USB2 performs better overall. It does depend on how busy your computer is.
Yeah I figured there’s no difference between a $2 cable and a $40 one. My mac mini only has one FW400 jack. I had my Drobo daisy-chained through another external drive that had both FW400 and FW800. I had no problems.
As soon as I dumped the other external drive and plugged the Drobo directly into the FW400 jack, it started doing wierd drops. I’d move the cable around a bit and I would see the drobo’s lights shut down and go into Standby mode.
I just wonder if the cable is bad or the Drobo doesn’t want to use a 400 to 800 adapter cable.
I was told that FW400 is ALWAYS better than USB2.0 for external drives. USB2.0 is good for bursty data whereas FW is better for constant streaming of my movies.
Can’t say specifically for Drobo, but my employer sells Firewire 400 devices, and we have seen problems with cheaper Firewire 400 to 800 cables, and especially with adapters. Our support recommends the Belkin cable, as it works well with our devices.
Firewire in general is picky about cables… Even with FW400 cables, I’ve seen cheap and expensive cables that work fine, and other cheap cables that don’t work well at all.