can something like a 2tb seagate barracuda be put in raid with a WD 2 tb green
It could be put into JBOD (just a bunch of disk). That is where the computer will see all the drives as one.
You can't use RAID 0/1/5/10 etc with mismatched drives
oh, ok. i was just wondering, since i was planning on building a new rig soon.
You can RAID with different drives (I personally wouldn't, but it CAN be done), however it is not recommended to use drives with different RPM. I definitely would not do it with a Green drive though as they utilize head parking at random times to "save power". This can cause the system to think the RAID has failed, and buhbye data.