i've been using a lacie 500gb "big disk extreme with triple interface" on the mac mini hooked up to my tv to hold all of my movies. it died the other day and wouldn't attach to the mac. since it was out of warranty anyway, i opened it up to see what was happening.
it's a big unit since it has two 250gb drives in it that are concatenated as one 500gb drive to the operating system. when plugging it in, the drives would whirr up very faintly but nowhere near full speed. the blue light on the enclosure would blink and then go solid for a second, then keep blinking as if it was continuously trying to read from the drives to attach to the mac.
i unplugged each of the drives to let each one power up by itself and each one made the same noise. i figured that the chance of both drives suffering a motor or other failure at the exact same time was unlikely, so i came to the conclusion that the enclosure's internal board was not sending enough power to the drives to get them to spin up.
if there had just been one drive in the unit, i could have just put it in another computer and copied all the data off, but since the drives are concatenated by the enclosure, they wouldn't be readable in anything other than the lacie unit.
i was preparing to file a support request with lacie to see if i could buy a refurbished replacement board or enclosure with no drives in it so i could recover my data. in doing so, i wanted to put the drives in another computer to make sure they would spin up and attach as separate drives just to confirm that the motors weren't broken. but then i quickly realized that i could just use the power cables from that computer to power up the drives while leaving their ide cables connected to the enclosure so it could concatenate them and attach to my mac through its usb cable.
so i did that and the drives powered up, the enclosure attached the 500gb set to my mac, and i'm now rescuing all of my data.