what I found it is working:
- one sata connected drive mounted and running do not cause any problems for me (btrfs defrag + lxc containers running + media server + etc all running together )
- 2 drives on sata ports only sharing data on network ( cpu limits network transfers about 30MB/s and therefore pcie bus is not overloaded, no other services causing drives reading or writing than samba is not running )
- transfers between usb 3.0 drive and sata connected drives
- rsync between 2 drives with limited speed about 15MB/s (rsync --bwlimit=15M)
what is not working for me:
- raid sync between two drives on sata ports (drives transfers data at maximum speed about 300MB/s together and it causes kernel error and sata connected drives are out of game until router is restarted)
- “btrfs scrub” on two drives at once (same like previous note)
- copying data at full speed between drives on sata ports (same like previous notes)