Description
A Network Attached Storage (NAS) device is essentially an external hard drive connected to a network but with more features and capability of a standard external hard drive. The primary role of a NAS device is supplying a file-based data storage to other devices on the network. A NAS unit cannot carry out general-purpose computing tasks, although some may be technically possible to run other software on it. NAS units generally require a PC or laptop to connect to it to operate, configure etc and therefore are controlled over the network, often by a browser. For those who work in a company with an IT infrastructure might be familiar with this technology as this is analogous to a file server. A file server is essentially a NAS unit but has an Operating System (OS) to provide additional functionality and features.
Today’s NAS drives are capable of taking more than one hard drive so can be arranged into logical, redundant storage containers or RAID arrays (redundant arrays of inexpensive/independent disks). There are at least 9 types of RAID but the most common ones are:
- RAID-0: This technique has striping but no redundancy of data. It offers the best performance but no fault-tolerance.
- RAID-1: This type is also known as disk mirroring and consists of at least two drives that duplicate the storage of data. There is no striping. Read performance is improved since either disk can be read at the same time. Write performance is the same as for single disk storage. RAID-1 provides the best performance and the best fault-tolerance in a multi-user system.
- RAID-5: This type includes a rotating parity array. This means, all read and write operations can be overlapped. RAID-5 stores parity information but not redundant data (but parity information can be used to reconstruct data). RAID-5 requires at least three and usually five disks for the array. It's best for multi-user systems in which performance is not critical or which do few write operations.