You should always have additional USB just case you will have a problem with a USB hub that you are unable to repair and you are on a emergency deadline with a project.
This is not a backup drive, its a USB hub. Its designed to add more USB ports when you do not have enough for all of your devices.
It depends on the type of ports needed. If you need more USB sockets, you can simply plug a USB hub into a USB socket. However, if you need other types of ports (like display ports, network ports, 9 or 25-pin serial ports, SATA sockets etc)., or you don't want to use a USB hub, then you would have to install an expansion card.
If you are in need of more USB ports, you need to get a USB Hub. A USB Hub acts like a splitter - you connect it to one port, and the port itself allows you to connect several devices to it, rather than directly to the USB port on the PC.
A root hub is the socket on a computer's system board to which its USB ports are connected. A computer may have more than one USB root hub.
a USB hub
In regards to the average usb port hub and how many ports are available, this can vary. The average usb port hub can support up to four usb inputs at a time.
Buy a USB hub and connect to one of the USB ports. This splits any one USB port into 4 or 7 ports(depending on the model of hub).
There is no minimum or required number for USB ports on a laptop. Depending on the age and design of the laptop, it could be anywhere from zero to ten. I have seen only 2 USB ports on older laptops, most of the new ones atleast have 4 USB ports. Netbooks(10" & 11") have not more than 2 USB ports. If in anycase you need more USB ports, you could buy an USB hub for as less as 10$, which will add 4 more ports to your laptop.
A USB hub can be attached to any of the existing USB ports to provide additional connectors.
You want a USB hub.
Depends on the type of hub you're talking about. A USB expansion hub for example would allow for additional USB ports.
Not all USB mice will work with an adapter. If it did not originally ship with an adapter, that you lost and are now replacing, then odds are it will not work. A USB hub adding more USB ports may be a better solution.