I'll leave the performance discussion to the other thread on here. This is about stability.
If I have multiple sources of activity on a USB attached hard drive, the mounted fileshare will disappear. It's fixed by going into TomatoUSB and remounting the USB drive.
Downloading a torrent with Transmission to the USB attached hard drive while a PC is reading from that drive. It may take a few minutes or even ten or twenty minutes but the performance will degrade quickly and then the mount just disappears. This never seems to happen as long as I make sure only one thing is happening on a drive at a time.
Firmware: Tomato Firmware v1.28.9049 MIPSR2-beta19 K26 USB vpn3.6
Router: Asus RT-N16
Drive: Samsung 1TB 5400rpm "green" drive formatted with NTFS