Do you have a free PCIe slot?
If so, you can buy an external chassis for disks, (the chassis should include power
supply and cooling). Then use a SAS PCIe card with external connector(s), and
external cable(s) to the external chassis. Ideally the chassis uses a SAS port
expander. Thus, the connection between TS140 & external chassis uses the more
stable SAS protocol and potentially longer cables.
Please don't use an external chassis with SATA port multipler. They tend not to
work well, and are limited to 5 disks. Plus, they require both OS and SATA host
controller support.
Note that many people here don't recomend external trays, (even if they are SAS
connected). People get nervous because the external chassis / trays have separate
power cords and external data cables. Thus, subject to potential cable issues,
(knocking one loose can cause the ZFS pool to become off-line).