Disk Storage Architectures
Technology has evolved over the years to meet the exponential increase in the volume of data stored today. Network storage technologies enable you to store and manage information in an effective manner by allowing data to be readily accessed by client and server systems on the network.
SAN (Storage Area Network)
A SAN is a network of storage devices—such as disk arrays and automated tape libraries—that are connected to each other and to multiple servers or server clusters.
NAS (Network Attached Storage)
- IP SAN or iSCSI: sub-network based on a familiar Ethernet and the Internet Protocol (IP)
- Fibre Channel SAN: separate network based on high bandwidth Fibre Channel technology
NAS is a dedicated file server that connects to an IP/Ethernet network and is accessible by multiple clients and servers on a network.
Shared DAS (Direct Attached Storage)
- File/print: self-contained file/print server optimised for Windows environments
- Gateway: Windows- and UNIX-optimised file server that connects to a SAN Shared
DAS is a storage device—such as a disk array or tape system—that is cabled directly to a host server. While a DAS device is physically “captive” to its host server, it can be logically shared by multiple clients and servers on a network through standard network communication protocols.
iSCSI (SCSI commands sent via the Internet Protocol)
- SCSI: storage array that can attach to one or two servers
- Fibre Channel: storage array that can attach to up to eight servers and can scale into a SAN
The new storage protocol iSCSI is a standard that allows commands to be transmitted over Ethernet networks using the Internet Protocol (IP). This enables an iSCSI storage device to be attached to an existing network in order to create a SAN. While both iSCSI and NAS use IP and Ethernet to operate, they each perform unique tasks; NAS typically supports file (and sometimes print) services, whereas iSCSI is used with applications, such as database systems and email. Similarly, while iSCSI performance can be enhanced by new network adapter cards, Fibre Channel SANs are often used for high performance applications.