Data Center Using SAN/NAS

A data center  is a facility used to house computer systems and associated components, such as telecommunications and storage system. It generally includes redundant or backup power supplies, redundant data communications connections, environmental controls (e.g. air conditioning, fire supperssion) and security devices.

The TIA-942 describe the requirements for the data center infrastructure. The simplest is a Tire 1 data center, which is basically a computer room, following basic guidelines for the installation of computer systems. The most stringent level is a Tire 4 data center, which is designed to host mission critical computer systems, with fully redundant subsystems and compartmentalized security zones controlled by biometirc access controls methods. Another consideration is the placement of the data center in a subterranean context, for data security as well as environmental considerations such as cooling requirements. 

Network Attached Storage (NAS) is file level computer data storage connected to a computer network providing dta access to heterogeneous network clients.

NAS system contain one or more hard disks, often arranged into logical, redundant storage containers or RAID arrays (redundant arrays of inexpensive/independent disks). NAS removes the responsibility of file serving from other servers on the network.

Storage Area Network (SAN) is an architecture to attach remote computer storage devices (such as disk arrays, tape libraries, and optical jukeboxes) to serves in such a way that the devices appear as locally attached to the operating system. Although the cost and complexity of SANs are dropping, they are sitll uncommon outsdie larger enterprise. 

Most storage networks use the SCSI protocal for communication between servers and disk drive devices. they do not use SCSI low level physical interface (e.g cables), however, as its bus topology is unsuitable for networking. A mapping layer to other low level protocols is used to form a network:

- ATA over Ethernet (AoE), mapping of ATA over Ethernet.
- Fibre Channel over Ethernet (FCoE)
- iSCSI, mapping of SCSI over TCP/IP etc.

A NAS unit is essentially a self contained computer connected to a network, with the sole purpose of supplying file based data storage services to other devices on the network. The operating system and other software on the NAS unit provide the functionality of data storage, file system, and access to files, and the management of these functionalities. The unit is not designed to carry out general purpose computing taks, although it may technically be possible to run other software on it. NAS units usually do not have a keyborard or display, and are controlled and configured over the network, often by connecting a browser to their network address.


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