The HP Smart Array P841 Controller is a full height, PCIe 3 x 8, 12 Gb/s Serial Attached SCSI (SAS) RAID controller that provides enterprise-class storage performance, increased external scalability, and data protection for select HP Pro Liant Gen 9 rack & tower servers. It features 16 external physical links & delivers increased server uptime by providing advanced storage functionality, including online RAID level migration (between any RAID levels) with flash back write cache (FBWC), global online spare, and pre-failure warning. The Gen 9 family of controllers supports the HP Smart Storage Battery. With HP Smart Storage Battery, multiple Smart Array controllers are supported without needing additional backup power sources for each controller, resulting in simple upgrade process.