Linux software RAID 1 - root filesystem becomes read-only after a fault on one disk
Solution 1:
Your dmesg output should give you an indication as to why it's signalling failure to the PV; that shouldn't be happening. As far as getting the system writable again, kicking the VG and LV to read-only and then back to read-write works from memory, but the real resolution is getting md to stop worrying LVM unnecessarily.