Sure, will keep you updated.
One moment I already found, by using software RAID 1 (mdadm) on plain sata disks with lvm gives performance degradation, uses a lot of cpu time for syncing. On 8 core system load average was 2-4, after the switch to btrfs on same RAID1, reduced the load to 1-2.
But I keep testing the direct-lvm, might find the bottleneck