Direct Attached Storage (DAS)
Direct attached storage is the term used to describe a storage device that is directly attached to a host system. The simplest example of DAS is the internal hard drive of a server computer, though storage devices housed in an external box come under this banner as well. DAS is still, by far, the most common method of storing data for computer systems. Over the years, though, new technologies have emerged which work, if you'll excuse the pun, out of the box.
Network Attached Storage (NAS)
Network Attached Storage, or NAS, is a data storage mechanism that uses special devices connected directly to the network media. These devices are assigned an IP address and can then be accessed by clients via a server that acts as a gateway to the data, or in some cases allows the device to be accessed directly by the clients without an intermediary.
The beauty of the NAS structure is that it means that in an environment with many servers running different operating systems, storage of data can be centralized, as can the security, management, and backup of the data. An increasing number of companies already make use of NAS technology, if only with devices such as CD-ROM towers (stand-alone boxes that contain multiple CD-ROM drives) that are connected directly to the network.
Some of the big advantages of NAS include the expandability; need more storage space, add another NAS device and expand the available storage. NAS also bring an extra level of fault tolerance to the network. In a DAS environment, a server going down means that the data that that server holds is no longer available. With NAS, the data is still available on the network and accessible by clients. Fault tolerant measures such as RAID, which we'll discuss later), can be used to make sure that the NAS device does not become a point of failure.
Storage Area Network (SAN)
A SAN is a network of storage devices that are connected to each other and to a server, or cluster of servers, which act as an access point to the SAN. In some configurations a SAN is also connected to the network. SAN's use special switches as a mechanism to connect the devices. These switches, which look a lot like a normal Ethernet networking switch, act as the connectivity point for SAN's. Making it possible for devices to communicate with each other on a separate network brings with it many advantages. Consider, for instance, the ability to back up every piece of data on your network without having to 'pollute' the standard network infrastructure with gigabytes of data. This is just one of the advantages of a SAN which is making it a popular choice with companies today, and is a reason why it is forecast to become the data storage technology of choice in the coming years.
Irrespective of whether the network storage mechanism is DAS, NAS or SAN, there are certain technologies that you'll find in almost every case. The technologies that we are referring to are things like SCSI and RAID. For years SCSI has been providing a high speed, reliable method for data storage. Over the years, SCSI has evolved through many standards to the point where it is now the storage technology of choice. Related, but not reliant on SCSI, is RAID. RAID (Redundant Array of Independent Disks) is a series of standards which provide improved performance and/or fault tolerance for disk failures. Such protection is necessary as disks account for 50% of all hardware device failures on server systems. Like SCSI, RAID, or the technologies used to implement it, have evolved, developed and matured over the years.
In addition to these mainstays of storage technology, other technologies feature in our network storage picture. One of the most significant of these technologies is Fibre channel (yes, that that's fiber with an 're'). Fibre Channel is a technology used to interconnect storage devices allowing them to communicate at very high speeds (up to 10Gbps in future implementations). As well as being faster than more traditional storage technologies like SCSI, Fibre Channel also allows for devices to be connected over a much greater distance. In fact, Fibre Channel can be used up to six miles. This allows devices in a SAN to be placed in the most appropriate physical location.
Direct attached storage is the term used to describe a storage device that is directly attached to a host system. The simplest example of DAS is the internal hard drive of a server computer, though storage devices housed in an external box come under this banner as well. DAS is still, by far, the most common method of storing data for computer systems. Over the years, though, new technologies have emerged which work, if you'll excuse the pun, out of the box.
Network Attached Storage (NAS)
Network Attached Storage, or NAS, is a data storage mechanism that uses special devices connected directly to the network media. These devices are assigned an IP address and can then be accessed by clients via a server that acts as a gateway to the data, or in some cases allows the device to be accessed directly by the clients without an intermediary.
The beauty of the NAS structure is that it means that in an environment with many servers running different operating systems, storage of data can be centralized, as can the security, management, and backup of the data. An increasing number of companies already make use of NAS technology, if only with devices such as CD-ROM towers (stand-alone boxes that contain multiple CD-ROM drives) that are connected directly to the network.
Some of the big advantages of NAS include the expandability; need more storage space, add another NAS device and expand the available storage. NAS also bring an extra level of fault tolerance to the network. In a DAS environment, a server going down means that the data that that server holds is no longer available. With NAS, the data is still available on the network and accessible by clients. Fault tolerant measures such as RAID, which we'll discuss later), can be used to make sure that the NAS device does not become a point of failure.
Storage Area Network (SAN)
A SAN is a network of storage devices that are connected to each other and to a server, or cluster of servers, which act as an access point to the SAN. In some configurations a SAN is also connected to the network. SAN's use special switches as a mechanism to connect the devices. These switches, which look a lot like a normal Ethernet networking switch, act as the connectivity point for SAN's. Making it possible for devices to communicate with each other on a separate network brings with it many advantages. Consider, for instance, the ability to back up every piece of data on your network without having to 'pollute' the standard network infrastructure with gigabytes of data. This is just one of the advantages of a SAN which is making it a popular choice with companies today, and is a reason why it is forecast to become the data storage technology of choice in the coming years.
Irrespective of whether the network storage mechanism is DAS, NAS or SAN, there are certain technologies that you'll find in almost every case. The technologies that we are referring to are things like SCSI and RAID. For years SCSI has been providing a high speed, reliable method for data storage. Over the years, SCSI has evolved through many standards to the point where it is now the storage technology of choice. Related, but not reliant on SCSI, is RAID. RAID (Redundant Array of Independent Disks) is a series of standards which provide improved performance and/or fault tolerance for disk failures. Such protection is necessary as disks account for 50% of all hardware device failures on server systems. Like SCSI, RAID, or the technologies used to implement it, have evolved, developed and matured over the years.
In addition to these mainstays of storage technology, other technologies feature in our network storage picture. One of the most significant of these technologies is Fibre channel (yes, that that's fiber with an 're'). Fibre Channel is a technology used to interconnect storage devices allowing them to communicate at very high speeds (up to 10Gbps in future implementations). As well as being faster than more traditional storage technologies like SCSI, Fibre Channel also allows for devices to be connected over a much greater distance. In fact, Fibre Channel can be used up to six miles. This allows devices in a SAN to be placed in the most appropriate physical location.
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