The HP Smart Array P421 Controller is a low profile, 6 Gb/s, PCIe 3.0, Serial Attached SCSI (SAS) RAID controller that provides enterprise class, second generation storage performance, maximum external scalability, and data protection for select HP ProLiant Gen8 rack servers and tower servers. It features eight external SAS ports and delivers increased server uptime by providing advanced storage functionality, including online RAID level migration (between any RAID levels) with flash back write cache, global online spare, and pre-failure warning. Data compatibility between HP Smart Array Controllers means customers can easily upgrade to future Smart Array Controllers. HP Smart Array Advanced Pack 2.0 firmware makes it easier for customers to protect their data with advanced functionality for this next generation of Smart Array controllers, including features such as RAID 1 ADM (Advanced Data Mirroring). Increased performance, scalability and data protection, with reduced initial setup time. Up to 3x performance improvement over past generation, using up to 2 GB DDR3-1333 cache memory. Greater scalability for explosive growth with up to 200 drives supported. Long term data retention with flash back write cache (FBWC) offered as a standard feature, up to 2 GB capacity. Support for RAID 0/1, 1+0, 5, 50, 6, 60; new predictive spare activation for improved rebuild and maximized uptime. Reduction in parity initialization from 45 days to 5 hours.