I have a very strange issue with samba... Download and upload from my openwrt samba share to/from other computers in the same gigabit network keep continuously go up and down for apparently no reason, i have another nas with samba and transfer speed is rock stable around 100/110 MB/s, also, openwrt ram memory buffer gets quickly full and remain full until files got full transfered. My openwrt server (where samba3 share is) is x64 build on a quad core with 8gb of ram. I tried many smb.conf tweaks that one can find on the internet, but with no luck at all.
Also, maybe it can be uselfull, when transfer just started it goes full speed until ram buffer is full, then almost stops at all, just to start full speed again for 2-3 seconds, then it goes down again, and so on.
Hdparm (direct and not) reports my drives can read and write at over 300MB/s, obviously I know I can't transfer faster than 100/110 MB/s because of the speed cap or gigabit network, but I would have at least 80MB/s and STABLE.