By having a network attached storage device with multiple hard drives not only provides lots of capacity for storage , it also afford you data redundancy provided you are willing to go for some of that capacity to replicate your data across several drives at once. When looking at a NAS device with multiple-drive support, always be sure that you can access the hard drive bays, and consider how complicated it is to add or remove a drive. Many NAS models make it relatively easy and tool-free by placing hard drives into special trays that slide into a drive bay, but some may require more effort, such as affixing drives to trays with screws or connecting power and data cables. A NAS device offers hot- or cold-swap capability. The former means you can add or change a drive while the network storage device is running, while the latter requires you to shut down first before making any such changes.