In computing, the proposed Internet Storage Name Service (iSNS) protocol allows automated discovery, management and configuration of iSCSI and Fibre Channel devices (using iFCP gateways) on a TCP/IP network.
iSNS provides management services similar to those found in Fibre Channel networks, allowing a standard IP network to operate in much the same way that a Fibre Channel storage area network does. Because iSNS is able to emulate Fibre Channel fabric services and manage both iSCSI and Fibre Channel devices, an iSNS server can be used as a consolidated configuration point for an entire storage network. However, the use of iSNS is optional for iSCSI while it is required for iFCP. Additionally, an iSNS implementation is not required by the standard to provide support for both of these protocols. [1]
The iSNS standard defines four components:
An iSNS implementation provides four primary services:
iSNS implementations allow all entities in a storage network to register and query an iSNS database. Both targets and initiators can register with the iSNS database, and each entity can inquire about other initiators and targets. For example, a client initiator can obtain information about target devices from an iSNS server.
Administrators can use the discovery domains to divide storage nodes into manageable, non-exclusive groups. By grouping storage nodes, administrators are able to limit the login process of each host to the most appropriate subset of targets registered with the iSNS, which allows the storage network to scale by reducing the number of unnecessary logins and by limiting the amount of time each host spends establishing login relationships.
Each target is able to use login control to delegate their access control and authorization policies to an iSNS server. Such delegation is intended to promote centralized management.
The state-change notification (SCN) service allows an iSNS server to issue notifications about each event that affects storage nodes on the managed network. Each iSNS client may register for notifications on behalf of its storage nodes, and each client is expected to respond according to its own requirements and implementation.
Because the iSNS database stores naming and discovery information about both Fibre Channel and iSCSI devices, iSNS servers are able to store mappings of Fibre Channel devices to proxy iSCSI device images on the IP network. These mappings may also be made in the opposite direction, allowing iSNS servers to store mappings from iSCSI devices to proxy World Wide Names (WWNs).
Small Computer System Interface is a set of standards for physically connecting and transferring data between computers and peripheral devices, best known for its use with storage devices such as hard disk drives. SCSI was introduced in the 1980s and has seen widespread use on servers and high-end workstations, with new SCSI standards being published as recently as SAS-4 in 2017.
Internet Small Computer Systems Interface or iSCSI is an Internet Protocol-based storage networking standard for linking data storage facilities. iSCSI provides block-level access to storage devices by carrying SCSI commands over a TCP/IP network. iSCSI facilitates data transfers over intranets and to manage storage over long distances. It can be used to transmit data over local area networks (LANs), wide area networks (WANs), or the Internet and can enable location-independent data storage and retrieval.
Fibre Channel (FC) is a high-speed data transfer protocol providing in-order, lossless delivery of raw block data. Fibre Channel is primarily used to connect computer data storage to servers in storage area networks (SAN) in commercial data centers.
In computer hardware a host controller, host adapter or host bus adapter (HBA) connects a computer system bus which acts as the host system to other network and storage devices. The terms are primarily used to refer to devices for connecting SCSI, SAS, NVMe, Fibre Channel and SATA devices. Devices for connecting to FireWire, USB and other devices may also be called host controllers or host adapters.
In computer storage, a logical unit number, or LUN, is a number used to identify a logical unit, which is a device addressed by the SCSI protocol or by Storage Area Network protocols that encapsulate SCSI, such as Fibre Channel or iSCSI.
In computing, Serial Attached SCSI (SAS) is a point-to-point serial protocol that moves data to and from computer-storage devices such as hard disk drives and tape drives. SAS replaces the older Parallel SCSI bus technology that first appeared in the mid-1980s. SAS, like its predecessor, uses the standard SCSI command set. SAS offers optional compatibility with Serial ATA (SATA), versions 2 and later. This allows the connection of SATA drives to most SAS backplanes or controllers. The reverse, connecting SAS drives to SATA backplanes, is not possible.
In computer data storage, a SCSI initiator is the endpoint that initiates a SCSI session, that is, sends a SCSI command. The initiator usually does not provide any Logical Unit Numbers (LUNs).
The arbitrated loop, also known as FC-AL, is a Fibre Channel topology in which devices are connected in a one-way loop fashion in a ring topology. Historically it was a lower-cost alternative to a fabric topology. It allowed connection of many servers and computer storage devices without using then very costly Fibre Channel switches. The cost of the switches dropped considerably, so by 2007, FC-AL had become rare in server-to-storage communication. It is however still common within storage systems.
ATA over Ethernet (AoE) is a network protocol developed by the Brantley Coile Company, designed for simple, high-performance access of block storage devices over Ethernet networks. It is used to build storage area networks (SANs) with low-cost, standard technologies.
IPFC stands for Internet Protocol over Fibre Channel. It governs a set of standards created in January 2006 for address resolution (ARP) and transmitting IPv4 and IPv6 network packets over a Fibre Channel (FC) network. IPFC makes up part of the FC-4 protocol-mapping layer of a Fibre Channel system.
In Fibre Channel protocol, a registered state change notification (RSCN) is a Fibre Channel fabric's notification sent to all specified nodes in case of any major fabric changes. This allows nodes to immediately gain knowledge about the fabric and react accordingly.
Fibre Channel Protocol (FCP) is the SCSI interface protocol utilising an underlying Fibre Channel connection. The Fibre Channel standards define a high-speed data transfer mechanism that can be used to connect workstations, mainframes, supercomputers, storage devices and displays. FCP addresses the need for very fast transfers of large volumes of information and could relieve system manufacturers from the burden of supporting a variety of channels and networks, as it provides one standard for networking, storage and data transfer. Some Fibre Channel characteristics are:
A clustered file system (CFS) is a file system which is shared by being simultaneously mounted on multiple servers. There are several approaches to clustering, most of which do not employ a clustered file system. Clustered file systems can provide features like location-independent addressing and redundancy which improve reliability or reduce the complexity of the other parts of the cluster. Parallel file systems are a type of clustered file system that spread data across multiple storage nodes, usually for redundancy or performance.
Host-based zoning can include WWN or LUN masking, and is typically known as “persistent binding.”
On Linux, network block device (NBD) is a network protocol that can be used to forward a block device from one machine to a second machine. As an example, a local machine can access a hard disk drive that is attached to another computer.
Fibre Channel over Ethernet (FCoE) is a computer network technology that encapsulates Fibre Channel frames over Ethernet networks. This allows Fibre Channel to use 10 Gigabit Ethernet networks while preserving the Fibre Channel protocol. The specification was part of the International Committee for Information Technology Standards T11 FC-BB-5 standard published in 2009. FCoE did not see widespread adoption.
In computing the SCSI RDMA Protocol (SRP) is a protocol that allows one computer to access SCSI devices attached to another computer via remote direct memory access (RDMA). The SRP protocol is also known as the SCSI Remote Protocol. The use of RDMA makes higher throughput and lower latency possible than what is generally available through e.g. the TCP/IP communication protocol.
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 data 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).
iSCSI conformance testing is testing to determine whether an iSCSI Initiator/Target meets the iSCSI standard.
The Linux-IOTarget (LIO) is an open-source SCSI target implementation included with the Linux kernel. Internally, LIO does not initiate sessions, but instead provides one or more Logical Unit Numbers (LUNs), waits for SCSI commands from a SCSI initiator, and performs required input/output data transfers. LIO supports common storage fabrics, including FCoE, Fibre Channel, IEEE 1394, iSCSI, iSCSI Extensions for RDMA (iSER), SCSI RDMA Protocol (SRP) and USB. It is included in some Linux distributions and a storage option for cloud deployments due to its native support in QEMU/KVM, libvirt, and OpenStack.
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