When SAN is not SAN: new language for the SAN marketplace. (Storage Networking).We can decompose de·com·pose v. de·com·posed, de·com·pos·ing, de·com·pos·es v.tr. 1. To separate into components or basic elements. 2. To cause to rot. v.intr. 1. the acronym acronym: see abbreviation. A word typically made up of the first letters of two or more words; for example, BASIC stands for "Beginners All purpose Symbolic Instruction Code. , SAN, to identify three essential features of a SAN: "storage" nodes or resources, a physically and logically localized "area" in which those storage resources reside, and "network" connectivity. Storage nodes comprise -- storage devices (tape, disk drives) or subsystems (disk arrays, tape libraries) -- instead of compute To perform mathematical operations or general computer processing. For an explanation of "The 3 C's," or how the computer processes data, see computer. -- application or file servers. The localized area is physically and logically separate from a typical LAN (Local Area Network) A communications network that serves users within a confined geographical area. The "clients" are the user's workstations typically running Windows, although Mac and Linux clients are also used. on which clients run applications and hosts serve files. Finally, the connectivity among the components of the SAN is network-based. Storage device and subsystem A unit or device that is part of a larger system. For example, a disk subsystem is a part of a computer system. A bus is a part of the computer. A subsystem usually refers to hardware, but it may be used to describe software. interconnect (1) To attach one device to another. (2) A physical port (plug, socket) or wireless port (transmitter, receiver) used to attach one device to another. is via network media and protocol to many, possibly heterogeneous, sources and sinks of data instead of channel or bus attached to a single server. While these features are essential to the existence of a SAN, a SAN is much more than a collection of components. It must include control or management software that orchestrates connections and data transfer to achieve the desired functionality. A SAN, typically, provides block-based I/O (Input/Output) The transfer of data between the CPU and a peripheral device. Every transfer is an output from one device and an input to another. See PC input/output. I/O - Input/Output services, but may also support filebased I/O. The emphasis on block-level transactions is a convenience for and construct of data replication or backup software See backup program. (tool, software) backup software - Software for doing a backup, often included as part of the operating system. Backup software should provide ways to specify what files get backed up and to where. , because some see the primary value of the SAN as the domain in which backup of disk to tape might take place, independent of client-side activity. When backups are done in that automated fashion, there is no particular need for file-system involvement in moving data. However, there is also no particular reason to preclude the capability of file-level transactions occurring within the domain of a SAN. In fact, it is desirable to be able to mix both block- and file-level traffic to simultaneously accommodate both database and file system-attached clients. Furthermore, it is desirable to be able to mix heterogeneous storage resources within a SAN. So, what does the SAN acronym really describe? It is probably not very useful to say SAN is a product or a technology. Rather, it is more useful to describe SAN as a topology topology, branch of mathematics, formerly known as analysis situs, that studies patterns of geometric figures involving position and relative position without regard to size. or configuration or architecture aimed at achieving specific functions in an IT environment. While the description above is consistent with most others found in the literature, it really doesn't help one to understand either the full capability or the added value Added value in financial analysis of shares is to be distinguished from value added. Used as a measure of shareholder value, calculated using the formula:
For the sake of further discussion, we'll define a SAN as a configuration of components comprising three types of functional elements; devices, connectivity and control. The devices include storage devices or systems. The connectivity includes interconnection in·ter·con·nect v. in·ter·con·nect·ed, in·ter·con·nect·ing, in·ter·con·nects v.intr. To be connected with each other: The two buildings interconnect. v.tr. , routing, switching, media, and protocol. The control includes management of storage resources, data paths, data, and data transfer. Why and How to Differentiate? Common terminology and understanding is important to market and technology advancement and for customer benefit. The most important reason to differentiate SANs by function or some other attribute is three-fold. First, it is better for customers, because vendors can provide more clearly defined functional specifications using new language. Second, it is better for vendors, because customers can supply more clearly defined functional requirements See information requirements and functional specification. (specification) functional requirements - What a system should be able to do, the functions it should perform. in terms of this new language. Finally, industry analysts can more accurately characterize the market when nomenclature nomenclature /no·men·cla·ture/ (no´men-kla?cher) a classified system of names, as of anatomical structures, organisms, etc. binomial nomenclature is more granular granular /gran·u·lar/ (gran´u-lar) made up of or marked by presence of granules or grains. gran·u·lar adj. 1. Composed or appearing to be composed of granules or grains. 2. and less ambiguous. Many attributes of a SAN configuration could be used for classification. They could be based on hardware or software, connectivity, or functionality. For example, one could classify a SAN in terms of hardware attributes; as in a 10-node SAN, a 100TB SAN, or a disk-only SAN. One might also classify in terms of connectivity, such as a fiber-channel SAN, or a Gigabit Ethernet An Ethernet standard that transmits at 1 Gbps. Used mostly to connect high-end workstations and servers as well as for network backbones, Gigabit Ethernet transmits full duplex from point to point using switches and half duplex in a shared environment (CSMA/CD) using a hub. SAN. Finally, one might classify in terms of functional capability, as in a peer-managed SAN. Of course, there are many other possible classification schemes that could employ increasing levels of specificity by combining attributes or by deriving new figures of merit. For example, there might be a 100TB, Fibre-Channel SAN. Or, there might be a 100Mnode SAN, where Mnode is defined as data transfer capability in MB/sec. divided by the number of storage nodes in the SAN. The key is to provide some useful level of classification while avoiding too much specificity. This might be achieved by focusing more on what is provided, than by how it is provided. There is precedence The order in which an expression is processed. Mathematical precedence is normally: 1. unary + and - signs 2. exponentiation 3. multiplication and division 4. for this kind of language in the IT industry. For example, disk arrays are classified according to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. RAID levels. RAID levels are defined by functional characteristics and elements of the system. The Figure of Merit Noun 1. figure of merit - a numerical expression representing the efficiency of a given system, material, or procedure efficiency - the ratio of the output to the input of any system (Level) is related to functionality. Therefore, it may be useful to define SAN classes based on elements and function. SAN Classes The higher class number must include all of the attributes of the lower class numbers. Class numbers increase with complexity of the configuration and increased functional capability. The detailed class definitions that follow are being proposed as a starting point Noun 1. starting point - earliest limiting point terminus a quo commencement, get-go, offset, outset, showtime, starting time, beginning, start, kickoff, first - the time at which something is supposed to begin; "they got an early start"; "she knew from the for common SAN nomenclature for the IT industry. Several terms used in the class definitions are defined as follows: H/C H/C Hydrocarbon H/C Handicapped H/C Helicopter H/C Homecoming H/C Hand Controller H/C Hover Craft LAN: Host/Client network on which applications are run and files are served, primary traffic between nodes is message or file-based. SAN Server: Provides connectivity between H/C LAN and SAN, may perform other resource and data management functions; might be integrated as intelligent switch, domain manager or within a storage system. SAN Element: Any component of a SAN, e.g. server, switch, router, hub, storage resource, or software agent. SAN Class 1 * SAN server connected to an H/C LAN. * Multiple storage resources connected to the SAN server via a network media and protocol. * Must support communication among elements via block or device-level commands and may also support file-level access. SAN Class 2 * Multiple SAN servers connected to an H/C LAN. * Multiple, heterogeneous storage resources connected to the SAN server via a network media and protocol. * Must support communication among elements via block or device-level commands and may also support file-level access. SAN Class 3 * Multiple SAN servers connected to an H/C LAN. * Multiple, heterogeneous storage resources connected to the SAN server via a network media and protocol. * Must support communication among elements via block or device-level commands and may also support file-level access. * Provision of capability to transfer data directly from one storage resource to another under the control of a SAN element. SAN Class 4 * Multiple SAN servers connected to an H/C LAN. * Multiple, heterogeneous storage resources connected to the SAN server via a network media and protocol. * Must support communication among elements via block or device-level commands and may also support file-level access. * Provision of capability to transfer data directly from one storage resource to another under the control of a SAN element. * Provision of capability to represent part of, or more than one, physical storage resource in a logically divided, combined, or altered manner under the control of a SAN element. SAN Class 5 * Multiple SAN servers connected to an H/C LAN. * Multiple, heterogeneous storage resources connected to the SAN server via a network media and protocol. * Must support communication among elements via block or device-level commands and may also support file-level access. * Provision of capability to transfer data directly from one storage resource to another under the control of a SAN element. * Provision of capability to represent part of, or more than one, physical storage resource in a logically divided, combined, or altered manner under the control of a SAN element. * Provision of capability to implement advanced functions, such as QOS and policy-based management See policy management. via the cooperation of intelligent, peer-communicating, storage resources. A SAN is not a SAN. What a SAN does is more important than what a SAN is. Language that more clearly and specifically define the function and features of a SAN through the use of modifiers to the term "SAN" is needed. This kind of differentiation of SANs by classes can have value for both vendors and customers. The ideas presented for SAN classes in this article may be a useful starting point for industry-standard SAN class definitions. Marty Frary is an independent consultant with over 23 years experience performing research, product development and analysis in a variety of technologies and industries. This article is copyrighted by the author and is being used with permission. |
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