How to daemonize a shell task?
How can I run a console command (like cp or tar, for example) without needing to keep an open SSH?
nohup command &
Depending on exactly what you want to do, screen may work out for you.
You can run the command with screen, screen command then detach that screen and terminate your ssh session. Whatever is running in that screen session will still run, and you can re-attach to that session later, from another terminal.
When running commands remotely with ssh the -T option will also help.