Hey buddies, I have installed DSM4.1 (DS3612xs, build2668) on my DIY box (with onboard NIC chipset RT8111F), and I have created 1 volume with 4 HDDs running Raid5. And now I'd like to upgrade the system to DSM4.2 (DS3612xs build3211). I'm wondering whether backup data is necessary. If the upgrade will continue recognizing my volume? Is it risky to upgrade the system without data backup? Thanks!