Network storage devices Network Attached Storage, NAS

NAS (Network Attached Storage) is the separate integrated disk system. NAS-cerver, with the specialized OS and a set of useful functions of quick start of a system and ensuring access to files. A system is connected to a normal computer network (LAN), and is fast solution of the problem of shortage of the free disk space available to users of this network.

NAS is the storage connected to network as any network device, provides file data access. NAS devices are a combination of DWH and the server to which it is connected. In the simplest option the NAS device is the normal network server providing file resources.

History

Development of network technologies led to emergence of two network solutions for DWH – networks of storage Storage Area Network (SAN) for data exchange at the level of the blocks supported by client file systems and servers for data storage at the file Network Attached Storage (NAS) level. To distinguish traditional DWH from network one more retronym – Direct Attached Storage (DAS) was offered.

DAS, SAN and NAS appearing in the market consistently reflect the evolving chains of communications between the applications using data, and bytes in the carrier, containing these data. Once programs-applications were read and wrote blocks, then drivers as a part of the operating system appeared. In modern DAS, SAN and NAS the chain consists of three links: the first link – creation of RAIDs, the second – processing of the metadata allowing to interpret binary data in the form of files and records, and the third – services for providing data to the application. They differ on where and as these links are implemented. In a case with DAS DWH is "naked", it only gives an opportunity of storage and data access, and all the rest becomes on server side, starting with interfaces and the driver. With the advent of SAN providing RAID is transferred to the party of DWH, all the rest remains the same as in a case with DAS. And NAS differs in the fact that also metadata for ensuring file access are transferred to DWH besides, here the client needs only to support services of data.

Emergence of SAN became possible after in 1988 the Fibre Channel protocol (FC) was developed and in 1994 ANSI as the standard is approved. The term Storage Area Network is dated 1999. Over time FC gave way to Ethernet, and IP-SAN networks with connection on iSCSI gained distribution.

The idea of the network server of storage of NAS belongs to Brian Rendell from the Nyyukestla University and is implemented in machines on the UNIX-SERVER in 1983. This idea turned out so successful that it was picked up by a set of the companies, including Novell, IBM, and Sun, but finally replaced leaders of Netapp and EMC.

In 1995 Garth Gibson developed the principles of NAS and created object DWH (Object Storage, OBS). It began with the fact that separated all disk transactions into two groups, one entered executed more often, such as read and write, another more rare, such as transactions with names. Then he offered one more container in addition to blocks and files, he called it an object.

OBS differs in new type of the interface, it is called object. Customer services of data interact with metadata on object API (Object API). Not only data are stored in OBS, but also RAID is supported, the metadata relating to objects are stored and the object interface is supported. DAS, both SAN, and NAS, and OBS coexist in time, but each of access types corresponds to a certain data type and applications to a large extent.

In more detail about evolution of DWH read here.

Architecture of NAS

The NAS devices which are often called by fayler consist of the uniform head device executing data processing and performing network connection of a chain of disks. NAS devices allow to use storage systems on the Ethernet networks, in them the TCP/IP protocol is applied to the organization of shared access to files. These devices allow clients to share files even if the client systems work running different OS. Unlike architecture of DAS, in the NAS systems it is not required to transfer servers to a standalone mode for increase in the general capacity; disks can be added to structure of NAS simple connection of the device in network.

Scheme of connection of NAS

The NAS technology (network storage device subsystems, Network Attached Storage) develops as an alternative to the universal servers bearing a set of functions (printings, applications, the fax the server, e-mail, etc.). Unlike them NAS devices perform only one function - a file server. Also try to make it as it is possible better, more simply and quicker.

NAS are connected to LAN and provide data access for an unlimited number of heterogeneous clients (clients with different OS) or other servers. Now practically all NAS devices are focused on use in networks Ethernet Fast Ethernet Gigabit Ethernet () on the basis of protocols TCP/IP. Access to NAS devices is made using special file access protocols. The most widespread protocols of file access are protocols CIFS, NFS and DAFS. In similar servers stand specialized OS, such as MS Windows Storage Server.

Advantages and shortcomings

Pluses

• Low cost and availability of its resources not only to separate servers, but also to any computers of the organization
• Simplicity of collective use of resources
• Simplicity of deployment and administration
• Universality for clients (one server can service clients of MS, Novell, Mac, Unix)

NAS devices are very good in the heterogeneous environment where the fast file data access at the same time is necessary for many clients, including protocols TCP/IP CIFS NFS FTP TFTP , etc. Also high reliability of storage and flexibility of management in combination with simplicity of service is provided. As names of files may contain characters of different languages, many NAS provide support of codings UTF-8 Unicode.

NAS devices can be simplest "boxes" with one port Ethernet and two hard drives in RAID1 up to the huge systems with a large number of disks and external Ethernet-ports, several specialized servers. Sometimes NAS devices are a part of SAN network and have no own drives but only provide file data access, being on block devices of storage. In this case NAS undertakes function of the powerful specialized server, and SAN are data storage devices. We receive the topology of DAS grouped from NAS-and SAN components.

Minuses

• Information access through protocols of 'network file systems' often more slowly, than as to a local disk.
• The majority of inexpensive NAS servers do not allow to provide the high-speed and flexible data access method at the level of the blocks inherent in SAN systems, but not at the level of files.

The main lack of NAS consists in the raised load of network. For connection with network it is usually used several gigabit Ethernet-controllers working in a full duplex and though thus the due data exchange rate on network Wednesday is reached, load of network increases. Therefore it is previously necessary to calculate arrangement and the number of NAS devices.

NAS are widespread much less, than SAN devices, but the share of such systems constantly grows due to replacement of DAS.

Forecast of growth of the market

On April 5, 2012 Global Industry Analysts published the report of Network Attached Storage Devices: A Global Strategic Business Report in which designated the main points and the reasons of growth of on-line architecture of data storage. According to research company, information volumes in the world annually increase by 65% and till 2020 will reach 3 million petabyte. Natural growth of investments into storage systems and data backup is a consequence of it.

Especially popular in light outlined trend the architecture of NAS is. She does not demand high maintenance expenses and provides high data availability, sufficient performance level, transparency for end users, platform independence.

The volume of global market of NAS solutions till 2017 will reach $7 billion. The biggest piece of pie is the share of North America, however the Pacific Rim in the next six years will show enviable annual growth rates at the level of 14.1% too.

Until recently NAS was considered as a prerogative of representatives of small and medium business who traditionally locate very limited IT budgets. However authors of the report note that NAS solutions for needs of large enterprises begin to develop increasing number of vendors.

In the next several years in process of distribution of cloud computing the market expects this boom. At the same time proposed solutions will become is technically more perfect, so it is more attractive to customers. The key directions for development are availability, a mnogoarendnost and security.

The report of Global Industry Analysts includes the analysis of activity of 80 main and niche players of the market of NAS solutions, including, Buffalo, Dell, EMC, Isilon Systems, HP, 3Par, HDS, IBM, LSI, NetApp, Netgear, Oracle, SGI.

See Also

• Software-defined storage (Software-Defined Storage, SDS)
• Direct Attached Storage, DAS
• Storage area network (Storage Area Network, SAN)
• Product catalog and projects of DWH
• Data backup

• Andrey Zakharov, Main systems of data storage and their feature
• Storage area networks
• NAS is network system of data storage