In addition to standard storage and traditional tape-based backup technologies explained in Chapter X, businesses employ advanced storage technologies in order to achieve higher levels of applications and data availability. Most widely used advanced storage technologies such as direct access storage (DAS), storage area network (SAN), network attached storage (NAS), RAID technology, mirroring and data replication, data vaulting, continuous data protection, and clustering are explained in Chapter XI.
TopDas, San, And Nas
Direct access storage, storage area network, and network access storage technologies are briefly explained in this section.
Contemporary business is forced to cope with demands for more efficient and effective storage solutions as part of its efforts to recover faster and more efficiently from any type of failure and/or disaster. Apart from standard backup technologies, business computing employs additional technologies in finding the ways of managing data in an efficient and effective way. With advances in data communications, networking technologies and high speed coomunication lines, in addition to traditional primary storage technologies, several new approaches called “advanced storage systems” have been developed.
Most widely used advanced storage technologies are: a) direct access storage, b) storage area network (SAN), and c) network attached storage (NAS).
SAN and NAS technologies are mainly based on a) Fibre Channel as a mature storage backbone technology and/or b) newly developed Internet SCSI (iSCSI) and Serial ATA technologies. SANs that use iSCSI protocol are gaining acceptance as a supplement or even complete replacement for Fibre Channel-based SANs. Today, these storage solutions and services are being integrated into server operating platforms. For instance, HP decided to integrate Smart Array serial controllers, storage enclosures, Hot-Plug Serial Attached SCSI and Serial ATA hard drivers with HP ProLiant servers (Singer, 2005). Such an operating environment does not require separate connection devices/protocols for interconnecting servers, storage, networking devices. Support for storage scalability includes support for RAID systems and scalability clustering options.
Direct access storage (DAS) is a solution that is based on a direct connection between a server and its storage system (see Figure 1). Hard disk installed on a standard computer is also considered as a direct access storage system. This approach does not use a lot of networking devices, it is implemented onsite. Hence, it is characterized as a high performance solution with regard to data transfer rates. Several technologies are used within this model of storing data:
Figure 1. Direct attached storage (DAS)
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SCSI (Small Computer System Interface)
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RAID systems (Redundant Array of Independent/Inexpensive Disks)
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Serial or Serial Attached SCSI—SAS
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Fibre Channel technology.
Storage area network approach is based on sharing a storage system among several servers and storage devices by using SCSI, iSCSI, and Fibre Channel communication technology. Remote storage devices (disks, disk arrays, tape devices, tape libraries) can be attached to servers. SAN model uses file-based protocols such as NFS, SMB-SAMBA (Small/Server Message Block) and CIFS that allow attaching and sharing file systems over the network.
Storage area network is a network that is usually isolated from the local area networks and wide area networks. It employs high-speed networking technologies (Gigabits/sec).
NFS is an acronym for network file system developed by Sun and is used as a main networking platform on UNIX servers and workstations. Another product called NIS (network information services) was also developed by Sun and is distributed today together with NFS, in the form of NFS/NIS protocol. A version for connecting PCs called PCNFS was developed as well and is used in order to connect PCs to UNIX/Linux servers and share file systems.
SAMBA is a distributed as an open source code under the GNU General Public License system (www.samba.org). It is available for most UNIX versions including: HP-UX, AIX, IRIX, Solaris, SunOS, Ultrix, NetBSD, FreeBSD, OpenBSD, SCO-UNIX, proprietary systems such as OpenVMS and IBM MVS (OS/390—z/OS). It is supported by Linux community, as well. SAMBA is used as a powerful tool for interoperability between UNIX/Linux servers, proprietary servers and Windows-based servers and clients. However, this protocol can be used as a platform for SAN platforms.