Overview On Storage Devices SAN, DAS, NAS.

December 15, 2010 / Web Hosting

Storage is one of the most important are of concern for any of the people who surf online. In Storage variety of storage interconnects options, the various storage interconnects should be introduced. With the storage the connectivity is also too much important as the most widely know and used are Fibre Channel and iSCSI.

In internet the first Fibre Channel, or Fibre Channel-Arbitrated Loop (FC-AL), is a high-speed storage interconnect standard that provides up to 400 MBps of bandwidth (4 Gbps) in a given Fibre Channel segment or loop. There are other option to the client which is FC-AL as with FC-AL client can support up to 126 devices with host to server up to a distance of 10 km.

SCSI over IP

SCSI over IP, or Internet SCSI (iSCSI) which is an IP based storage interconnect standard that will give a complete alternative to its traditional Fibre Channel which is a SAN fabrics by using standard networking hardware Ethernet to create the back-end storage network.ISCSI provides connectivity speed from 1 Gigabit with 10 Gigabit on the way.

Fibre Channel typically out-performs iSCSI but for many cases, the performance of iSCSI is adequate and the storage industry is experiencing a shift towards iSCSI deployment. These two storage interconnects provide the necessary path for SCSI storage commands to be encapsulated and sent from the host to the storage controller for processing.

Brief On SAN, DAS, NAS

Storage Area Networks (SAN) are a type of storage device, as the name implies, back-end storage networks that connect multiple hosts through a switched fabric such as Fibre Channel or iSCSI, where as with (DAS) involves the direct connection of servers to storage. With an internal DAS controller solution, only the host server has access to the storage and therefore owns all of the connected storage.

Clustering is also supported with shared DAS storage where the clustering software determines which server can see a particular logical disk at any one time. Network Attached Storage (NAS) differs considerably from DAS and SAN. A NAS basically a file server and storage that often integrates an optimized operating system dedicated to file sharing. Clustering is supported with a SAN in a similar fashion as DAS via shared logical drives.


A SAN’s architecture works in a way that makes all storage devices available to all servers on a LAN or WAN. SAN is a dedicated network that is separate from LANs and WANs. It is basically used to connect all the storage resources to get connected to various servers.

SANs originated to overcome the problems with network attached storage (NAS) devices, which – like ordinary servers – are difficult to manage and difficult to expand the capacity on. NAS devices also add to the traffic on the network and suffer from the delays introduced by the operating systems’ network stacks.

It consists a big collection of SAN Hardware and SAN software where as these hardware typically has high inter-connection rates between the various storage devices and the software manages, monitors and configures the SAN with high-speed sub network of shared storage devices.

A storage device is a machine that contains nothing but a disk or disks for storing data. As more storage devices are added to a SAN, they too will be accessible from any server in the larger network. In this case, the server merely acts as a pathway between the end user and the stored data.

A SAN is a network of storage devices that are connected to each other and to a server…in some configurations a SAN is also connected to the network. … it is forecast to become the data storage technology of choice in the coming years.


Like traditional file servers which are available, NAS follows a client/server design. NAS which is Network Attached Storage client who use make a additional file server approach by creating systems designed specifically for data storage.

With the NAS technologies do follow the old but reliable client/server design. Just with a single hardware device, often called the NAS box or NAS head, acts as the interface between the NAS and network clients. These NAS devices doesn’t requires any type of monitoring from keyboard or mouse. It basically run an embedded operating system than a full-featured NOS.

The NAS appears on the network as a single “node” that is the IP address of the head device. NAS systems strive for reliable operation and easy administration. It also include built-in features such as disk space quotas, secure authentication, or the automatic sending of email alerts should an error be detected.

Clients always connect to the NAS head, however, rather than to the individual storage devices. A NAS can store any data that appears in the form of files, such as email boxes, Web content, remote system backups, and so on. Overall, the uses of a NAS parallel those of traditional file servers.


DAS is well established and widely adapted globally in the storage are. As the amount of personal usage on this type of storage devices are digital content is huge and rapidly growing. In digital content such as digital music, videos, photos, or any number of personal data, consumers need reliable and secure digital storage that is easily accessible.

Clustering is been supported with a SAN in a similar fashion like DAS via shared logical drives PLX is on of the leader in high-performance. DAS with powerful silicon, backed by our sophisticated software, firmware and applications, enable global OEMs/ODMs to deliver premium high-performance products that stand out amongst the crowd.

This technology is leveraged by PLX’s deep experience and understanding of USB, FireWire, PCI Express and eSATA connectivity, thus enabling storage system vendors to offer high value-added products to their customers.

Finally, though cluster solutions usually involve DAS or SAN, a NAS is preferred used with clustering if specific clustering requirements can be met.

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