A storage area network (SAN) or storage network is a computer network which provides access to consolidated, block-level data storage.SANs are primarily used to access storage devices, such as disk arrays and tape libraries from servers so that the devices appear to the operating system as direct-attached storage.A SAN typically is a dedicated network of storage devices not accessible through. NAS (network attached storage) fills in the gaps, acting as a central hub for all your photos, videos, music, and other files. But it requires you to connect your Mac to an external storage. A NAS drive that provides shared storage for everyone on your network is ideal for homes that own multiple Macs and mobile devices. Here are the 6 best NAS drives for Mac owners.
| Computer network types by spatial scope |
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| Fibre Channel | |
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| Layer 4. Protocol mapping | |
| LUN masking | |
| Layer 3. Common services | |
| Layer 2. Network | |
| Fibre Channel fabric Fibre Channel zoning Registered State Change Notification | |
| Layer 1. Data link | |
| Fibre Channel 8B/10B encoding | |
| Layer 0. Physical |
A storage area network (SAN) or storage network is a computer network which provides access to consolidated, block-level data storage. SANs are primarily used to access storage devices, such as disk arrays and tape libraries from servers so that the devices appear to the operating system as direct-attached storage. A SAN typically is a dedicated network of storage devices not accessible through the local area network (LAN).
Although a SAN provides only block-level access, file systems built on top of SANs do provide file-level access and are known as shared-disk file systems.
Storage architectures[edit]
Storage area networks (SANs) are sometimes referred to as network behind the servers[1]:11 and historically developed out of a centralized data storage model, but with its own data network. A SAN is, at its simplest, a dedicated network for data storage. In addition to storing data, SANs allow for the automatic backup of data, and the monitoring of the storage as well as the backup process.[2]:16–17 A SAN is a combination of hardware and software.[2]:9 It grew out of>ApplicationsSCSI LayerFCPFCPFCPFCPiSCSIiSERSRPFCIPiFCPTCPRDMA TransportFCoEIPIP or InfiniBand NetworkFCEthernetEthernet or InfiniBand Link
Software[edit]
A SAN is primarily defined as a special purpose network, the Storage Networking Industry Association (SNIA) defines a SAN as 'a network whose primary purpose is the transfer of data between computer systems and storage elements'. But a SAN does not just consist of a communication infrastructure, it also has a software management layer. This software organizes the servers, storage devices, and the network so that data can be transferred and stored. Because a SAN is not a direct attached storage (DAS), the storage devices in the SAN are not owned and managed by a server.[1]:11 Potentially the data storage capacity that can be accessed by a single server through a SAN is infinite, and this storage capacity may also be accessible by other servers.[1]:12 Moreover, SAN software must ensure that data is directly moved between storage devices within the SAN, with minimal server intervention.[1]:13
Network Storage Devices For Home
SAN management software is installed on one or more servers and management clients on the storage devices. Two approaches have developed to SAN management software: in-band management means that management data between server and storage devices is transmitted on the same network as the storage data. While out-of-band management means that management data is transmitted over dedicated links.[1]:174 SAN management software will collect management data from all storage devices in the storage layer, including info on read and write failure, storage capacity bottlenecks and failure of storage devices. SAN management software may integrate with the Simple Network Management Protocol (SNMP).[1]:176
In 1999 an open standard was introduced for managing storage devices and provide interoperability, the Common Information Model (CIM). The web-based version of CIM is called Web-Based Enterprise Management (WBEM) and defines SAN storage device objects and process transactions. Use of these protocols involves a CIM object manager (CIMOM), to manage objects and interactions, and allows for the central management of SAN storage devices. Basic device management for SANs can also be achieved through the Storage Management Interface Specification (SMI-S), were CIM objects and processes are registered in a directory. Software applications and subsystems can then draw on this directory.[1]:177 Management software applications are also available to configure SAN storage devices, allowing, for example, the configuration of zones and logical unit numbers (LUNs).[1]:178
Ultimately SAN networking and storage devices are available from many vendors. Every SAN vendor has its own management and configuration software. Common management in SANs that include devices from different vendors is only possible if vendors make the application programming interface (API) for their devices available to other vendors. In such cases, upper-level SAN management software can manage the SAN devices from other vendors.[1]:180
Filesystems support[edit]
In a SAN data is transferred, stored and accessed on a block level. As such a SAN does not provide data file abstraction, only block-level storage and operations. But file systems have been developed to work with SAN software to provide file-level access. These are known as shared-disk file system (SAN file system).Server operating systems maintain their own file systems on their own dedicated, non-shared LUNs, as though they were local to themselves. If multiple systems were simply to attempt to share a LUN, these would interfere with each other and quickly corrupt the data. Any planned sharing of data on different computers within a LUN requires software, such as SAN file systems or clustered computing.
In media and entertainment[edit]
Video editing systems require very high data transfer rates and very low latency. SANs in media and entertainment are often referred to as serverless due to the nature of the configuration which places the video workflow (ingest, editing, playout) desktop clients directly on the SAN rather than attaching to servers. Control of data flow is managed by a distributed file system such as StorNext by Quantum.[7] Per-node bandwidth usage control, sometimes referred to as quality of service (QoS), is especially important in video editing as it ensures fair and prioritized bandwidth usage across the network.
Quality of service[edit]
SAN Storage QoS enables the desired storage performance to be calculated and maintained for network customers accessing the device.Some factors that affect SAN QoS are:
- Bandwidth – The rate of data throughput available on the system.
- Latency – The time delay for a read/write operation to execute.
- Queue depth – The number of outstanding operations waiting to execute to the underlying disks (traditional or solid-state drives).
QoS can be impacted in a SAN storage system by an unexpected increase in data traffic (usage spike) from one network user that can cause performance to decrease for other users on the same network. This can be known as the 'noisy neighbor effect.' When QoS services are enabled in a SAN storage system, the 'noisy neighbor effect' can be prevented and network storage performance can be accurately predicted.
Using SAN storage QoS is in contrast to using disk over-provisioning in a SAN environment. Over-provisioning can be used to provide additional capacity to compensate for peak network traffic loads. However, where network loads are not predictable, over-provisioning can eventually cause all bandwidth to be fully consumed and latency to increase significantly resulting in SAN performance degradation.
:max_bytes(150000):strip_icc()/netgear-nas-drive-ces-2016-575c1fd25f9b58f22ec7cefa.jpg "Network storage devices for home")
Storage virtualization[edit]
Storage virtualization is the process of abstracting logical storage from physical storage. The physical storage resources are aggregated into storage pools, from which the logical storage is created. It presents to the user a logical space for data storage and transparently handles the process of mapping it to the physical location, a concept called location transparency. This is implemented in modern disk arrays, often using vendor-proprietary technology. However, the goal of storage virtualization is to group multiple disk arrays from different vendors, scattered over a network, into a single storage device. The single storage device can then be managed uniformly.[citation needed]
See also[edit]
- ATA over Ethernet (AoE)
- Direct-attached storage (DAS)
- Host bus adapter (HBA)
- Massive array of idle disks (MAID)
- Network-attached storage (NAS)
- Redundant array of independent disks (RAID)
- SCSI RDMA Protocol (SRP)
- Storage Management Initiative – Specification – (SMI-S)
- Storage resource management (SRM)
References[edit]
- ^ abcdefghiJon Tate, Pall Beck, Hector Hugo Ibarra, Shanmuganathan Kumaravel & Libor Miklas (2017). 'Introduction to Storage Area Networks'(PDF). Red Books, IBM.CS1 maint: uses authors parameter (link)
- ^ abcdefghiNIIT (2002). Special Edition: Using Storage Area Networks. Que Publishing. ISBN9780789725745.CS1 maint: uses authors parameter (link)
- ^ abcdefghijklmnChristopher Poelker; Alex Nikitin, eds. (2009). Storage Area Networks For Dummies. John Wiley & Sons. ISBN9780470471340.
- ^Richard Barker & Paul Massiglia (2002). Storage Area Network Essentials: A Complete Guide to Understanding and Implementing SANs. John Wiley & Sons. p. 198. ISBN9780471267119.CS1 maint: uses authors parameter (link)
- ^'TechEncyclopedia: IP Storage'. Retrieved 9 December 2007.
- ^'TechEncyclopedia: SANoIP'. Retrieved 9 December 2007.
- ^'StorNext Storage Manager - High-speed file sharing, Data Management, and Digital Archiving Software'. Quantum.com. Retrieved 8 July 2013.
External links[edit]
- Introduction to Storage Area Networks Exhaustive Introduction into SAN, IBM Redbook