I've recently turned my old early 2009 quad core 2.66 GHz Mac Pro into a file and media server. I have four 4 TB hard drives with content on them, and soon I'll be adding a fifth. Add in a 2.5" SSD for my system and that's a total of six drives.
Currently several of these drives are in their own enclosures. But in order to maximize read and write speeds (especially since the 2009 Mac Pro doesn't have any USB 3 ports) I was thinking of putting all of these drives in the Mac Pro itself: four in the drive bays and then two in the optical drive bays.
However, I'm worried that my old Mac Pro may not properly handle dissipating the heat generated by all five hard drives in addition to heat from the CPU and motherboard. I haven't ever replaced any of its fans. I'm also curious if there are other reasons making all of these drives internal might shorten their life.
Is this a reasonable idea? What are the issues that I should be aware of so I can keep everything running smoothly?