This helped me to fix my NAS hanging regularly on copying big files.

system-wise
echo 1024 > /sys/block/sda/queue/max_sectors_kb
blockdev --setra 65536 /dev/sda
echo deadline > /sys/block/sda/queue/scheduler

samba-wise
oplocks = no
level2 oplocks = no

some notice using FTP copying process seems to work much more reliable. Haven't tried that though.

and this ( Read more... )