https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=804629#25 Actually, after some research and having run dozens of old kernel versions I came to the conclusion that this LVM/RAID1 shit NEVER WORKED PROPERLY. It's just unbelievable. This RAID1 feature was added to LVM2 in 2011. dm-raid1 support was added to the kernel in v3.1, around 2011 or 2012 too. I tried almost all the kernel versions since 3.1 and in most of them all I get at boot is some shit about "wrong ioctl" and "bad magic" instead of activated volume. Which volume, mind you, was created just fine in the same kernel version, and it even works -- until reboot! SO IN FIVE FUCKING YEARS THIS SHIT NEVER WORKED AND NOBODY GIVE A FUCK ABOUT IT! So much for all that fucking "bazaar" and shit! It happened to work only due to the bug introduced somewhere in 4.0, which, by unfortunate coincidence, was exactly when some poor fuckers like me choose to convert some of their LVM volumes to RAID1. And it worked somehow, but then - oops! - the bug was fixed! Sorry, I just frustrated as fuck. I can't believe it. "Linux is reliable", they said. "All bugs are shallow", they said... Five years to test. FIVE FUCKING YEARS!