While there exists many expensive 4 port controller cards, the Promise SATA 300 TX4 card is not that expensive (unavailable on newegg, $70 on amazon).
My Motherboard has 4 SATA ports on it, Is there a way short of buying an expensive RAID card to add more SATA drives and do a software raid still?
Why is a RAID card any less expensive than an external enclosure? 4 bay enclosures are pretty pricey on newegg.
A software RAID should have nothing to do with a controller card, hence the name "software RAID".
By the way, how many SATA drives are in there now and how many do you want to install?
What about getting an external 8-bay eSATA enclosure and putting drives in it? Will the OS see this and software raid? (linux)
This depends on the software installed on your machine (dependant drivers, etc) and the hardware controller in the enclosure. Quite possibly, yes.
If the controller card handles the RAID than the OS should recognize one drive. If it's the software/OS that handles the RAID, than possibly, but you need the software for it. Also, if the OS handles the RAID, the enclosure is essentially acting like a RAID card.
