No the active midplane doesn't support 6Gbps. It's 3Gbps only. Have you tried to upgrade the SROMBSASMP2 Hardware RAID firmware and the SR2625_1625UR Backplane HSC Firmware?
Thanks for your advice! After the raid firmware update negotiated link speed became 3 Gbps.
It's not critical now, but I can't apply SR2625_1625UR Backplane HSC Firmware update. In EFI Shell I receive following error after startup.nsh execution:
Loading IPMI driver: .\ipmi.efi
IPMI Driver is not initialized..
When I try to manually load ipmi.efi using shell command load ipmi.efi, it loads successfully, but subsequent execution of startup.nsh stops with an error
assertion "tmp != NULL" failed: file "sys\open.c", line 171
I'll be grateful for any help in solving this problem.
Did you extract the correct files to your USB drive? The name of the batch file is x625HSC217.nsh, not startup.nsh.
I'm very sorry. Of course, name of startup file is x625HSC217.nsh. I mean x625HSC217.nsh. I updated 2 servers in one evening 
OK that's weird... I'll try it next week.
I tried to upgrade to HSC 2.17 today, no issue seen. What's your BIOS/Firmware version? Update to 61;60;26 if you haven't done so.
