Thank You for contacting HPE support,
Please find the answers below
1> Before you proceed further please make sure the present Raid card is working fine if not you need the Replace the system Board since P410i is integrated to system board or you can install a PCI controller which is less expensive.
The server supports maximum of 16 HDD,s (please refer below quick specs page 6 under Maximum Internal Storage)
https://h20195.www2.hpe.com/v2/getdocument.aspx?docname=c04199811#
2> One controller has 2 ports and each port supports 4 Drives so 1 Raid card will support 8 drives ,Therefore you have 2 options either you can install 2 * Raid cards or use 1 Raid card with SAS expander so that it can support all 16 HDD,s
3> If present Raid card is faulty then you will have to Purchase PCI raid card (Required cache and battery)+ PCI SAS expander + SAS cable kit (Which normally comes with SAS expander )
A. SAS Expander
468406-B21 : HP 24 Bay 3Gb SAS Expander Card
B. Smart Array P410 Controller
462862-B21 : HP Smart Array P410/256 2-ports Int PCIe x8 SAS Controller
462864-B21 : HP Smart Array P410/512 BBWC 2-ports Int PCIe x8 SAS Controller
578230-B21 : HP Smart Array P410/512 FBWC 2-ports Int PCIe x8 SAS Controller
572532-B21 : HP Smart Array P410/1G FBWC 2-ports Int PCIe x8 SAS Controller
Thanks
HPE Support