Please forgive my dopey question: I have an elderly Mac Pro 2,1 2x3Gh Quad Core Xeon running OS 10.7.5 (Lion) with a 2 output PCIe card which allows me to use 8 external SATA drives in two StarTech toasters.
I have one spare 1x PCIe card slot. Other slots taken by Blackmagic and Radeon 5770.
Is it technically possible for me to run external Thunderbolt drives using some sort of PCIe card? Or would it be pointless anyway - reducing speed of Thunderbolt drive?
Unfortunately, there is no such beast (PCIe Thunderbolt adapter) that works with the Mac... Plus, you would need an x4 slot as a minimum to properly support even Thunderbolt 1. You could use an eSATA card like the Sonnet Tech Tempo 2 port eSATA card which would allow you to attach 2 more eSATA drives.
To expand that unit further, you would either need to update the drives in your StarTech units to larger disks or upgrade them to native SAS drive enclosures with expander support so that they can daisy chain allowing more drives per SAS channel.