My SSD is 500GB and I am constantly running out of space. Can I add a traditional higher quality hard drive to the pool? Or is this a bad idea? ShouldI just add another SSD of the same size?

Have you read this:

 

    http://lime-technology.com/wiki/index.php/UnRAID_6_2/Storage_Management#Cache_pool_operations

 

While it not specified discussed, the omission of a warning is significant.  However, I would be reluctant to add a HDD to form a SSD/HDD cache from a performance standpoint if for no other reason.  Remember to research what level of data protection (if any!) each version of the btrfs RAID option will provide you. 

 

And if you have further questions, you should tell us what version of unRAID you are using. 

Thanks Frank,

 

I am on the latest build. 6.2.2. I was considering a 1-2TB 10k HDD in with the SSD if I am opening a can of worms, its not that big of a deal I can get another SSD.