Thanks for the Reply
a pci commom sata board expansion look a good solution ? (no SAS board)
SATA Port Multipliers - I think is not a good solution 
lol
For right now I’ll remove the read cache , but when my pools area full, Will be a big problem
CMR HDD at local Market is too expensive , We talk about US$300,00 ~$400,00 for 8 TB (for mirror x2), but maybe there’ll the only way.
Option 2, I ll buy a chinese sas board with a FAN and dont leave my NAS ON 24 Hours per day , just switch on When a need copy or read files
Regards