SCSI Wikipedia. In computing, i.SCSI listenEYE skuz ee is an acronym for Internet Small Computer Systems Interface, an Internet Protocol IP based storage networking standard for linking data storage facilities.It provides block level access to storage devices by carrying SCSI commands over a TCPIP network.SCSI is used to facilitate 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.The protocol allows clients called initiators to send SCSI commands CDBs to storage devices targets on remote servers.It is a storage area network SAN protocol, allowing organizations to consolidate storage into storage arrays while providing clients such as database and web servers with the illusion of locally attached SCSI disks.It mainly competes with Fibre Channel, but unlike traditional Fibre Channel which usually requires dedicated cabling,a i.SCSI can be run over long distances using existing network infrastructure.SCSI was pioneered by IBM and Cisco in 1.March 2. 00. 0. 3ConceptseditIn essence, i.SCSI allows two hosts to negotiate and then exchange SCSI commands using Internet Protocol IP networks.Map Drive Using Microsoft Iscsi Initiator Download' title='Map Drive Using Microsoft Iscsi Initiator Download' />By doing this, i.SCSI takes a popular high performance local storage bus and emulates it over a wide range of networks, creating a storage area network SAN.Unlike some SAN protocols, i.SCSI requires no dedicated cabling it can be run over existing IP infrastructure.As a result, i. SCSI is often seen as a low cost alternative to Fibre Channel, which requires dedicated infrastructure except in its FCo.E Fibre Channel over Ethernet form.However, the performance of an i.SCSI SAN deployment can be severely degraded if not operated on a dedicated network or subnet LAN or VLAN, due to competition for a fixed amount of bandwidth.Although i. SCSI can communicate with arbitrary types of SCSI devices, system administrators almost always use it to allow server computers such as database servers to access disk volumes on storage arrays.SCSI SANs often have one of two objectives Storage consolidation.Organizations move disparate storage resources from servers around their network to central locations, often in data centers this allows for more efficiency in the allocation of storage, as the storage itself is no longer tied to a particular server.In a SAN environment, a server can be allocated a new disk volume without any changes to hardware or cabling.Disaster recovery.Organizations mirror storage resources from one data center to a remote data center, which can serve as a hot standby in the event of a prolonged outage. Type Of Location Update In Gsmarena . In particular, i.SCSI SANs allow entire disk arrays to be migrated across a WAN with minimal configuration changes, in effect making storage routable in the same manner as network traffic.InitiatoreditAn initiator functions as an i.SCSI client. An initiator typically serves the same purpose to a computer as a SCSI bus adapter would, except that, instead of physically cabling SCSI devices like hard drives and tape changers, an i.SCSI initiator sends SCSI commands over an IP network.An initiator falls into two broad types A software initiator uses code to implement i.SCSI. Typically, this happens in a kernel resident device driver that uses the existing network card NIC and network stack to emulate SCSI devices for a computer by speaking the i.SCSI protocol. Software initiators are available for most popular operating systems and are the most common method of deploying i.SCSI. A hardware initiator uses dedicated hardware, typically in combination with firmware running on that hardware, to implement i.SCSI. A hardware initiator mitigates the overhead of i.SCSI and TCP processing and Ethernet interrupts, and therefore may improve the performance of servers that use i.SCSI. An i. SCSI host bus adapter more commonly, HBA implements a hardware initiator.A typical HBA is packaged as a combination of a Gigabit or 1.Gigabit Ethernet network interface controller, some kind of TCPIP offload engine TOE technology and a SCSI bus adapter, which is how it appears to the operating system.An i. SCSI HBA can include PCIoption ROM to allow booting from an i.SCSI SAN. An i. SCSI offload engine, or i.SOE card, offers an alternative to a full i.SCSI HBA. An i. SOE offloads the i.SCSI initiator operations for this particular network interface from the host processor, freeing up CPU cycles for the main host applications.Map Drive Using Microsoft Iscsi Initiator Download' title='Map Drive Using Microsoft Iscsi Initiator Download' />SCSI HBAs or i.SOEs are used when the additional performance enhancement justifies the additional expense of using an HBA for i.SCSI,4 rather than using a software based i.SCSI client initiator.SOE may be implemented with additional services such as TCP offload engine TOE to further reduce host server CPU usage.The i. SCSI specification refers to a storage resource located on an i.SCSI server more generally, one of potentially many instances of i.SCSI storage nodes running on that server as a target.An i. SCSI target is often a dedicated network connected hard disk storage device, but may also be a general purpose computer, since as with initiators, software to provide an i.SCSI target is available for most mainstream operating systems.Common deployment scenarios for an i.SCSI target include Storage arrayeditIn a data center or enterprise environment, an i.SCSI target often resides in a large storage array.These arrays can be in the form of commodity hardware with free software based i.SCSI implementations, or as commercial products such as in Cloud.Map Drive Using Microsoft Iscsi Initiator Download' title='Map Drive Using Microsoft Iscsi Initiator Download' />ISCSI initiator, Virtual CDDVDRW Emulator, Virtual Encryption Disk and Virtual CDDVDROM Emulator AllinOne free software.Microsoft Sharepoint 2010 with VMware vSphere 5.FlexPod. Although iSCSI technology enables costeffective blockbased storage networking, its deployment has generally been restricted to SMBSME and departmental workgroup.Byte, Stor. Trends, Pure Storage, HP Storage.Works, Equal. Logic, Tegile Systems, Nimble storage, Reduxio, IBM Storwize family, Isilon, Net.App filer, EMC Corporation NS series, CX4, VNX, VNXe, VMAX, Hitachi Data Systems HNAS, or Pivot.STAC. A storage array usually provides distinct i.SCSI targets for numerous clients.Software targeteditNearly all modern mainstream server operating systems such as BSD, Linux, Solaris or Windows Server can provide i.SCSI target functionality, either as a built in feature or with supplemental software.Some specific purpose operating systems implement i.SCSI target support.Logical unit numbereditIn SCSI terminology, LUN stands for logical unit, which are specified by unique logical unit numbers.A LUN represents an individually addressable logical SCSI device that is part of a physical SCSI device target.In an i. SCSI environment, LUNs are essentially numbered disk drives.An initiator negotiates with a target to establish connectivity to a LUN the result is an i.SCSI connection that emulates a connection to a SCSI hard disk.Initiators treat i.SCSI LUNs the same way as they would a raw SCSI or IDE hard drive for instance, rather than mounting remote directories as would be done in NFS or CIFS environments, i.SCSI systems format and directly manage filesystems on i.SCSI LUNs. In enterprise deployments, LUNs usually represent subsets of large RAID disk arrays, often allocated one per client.SCSI imposes no rules or restrictions on multiple computers sharing individual LUNs it leaves shared access to a single underlying filesystem as a task for the operating system.Network bootingeditFor general data storage on an already booted computer, any type of generic network interface may be used to access i.SCSI devicescitation needed.However, a generic consumer grade network interface is not able to boot a diskless computer from a remote i.SCSI data sourcecitation needed.Instead, it is commonplace for a server to load its initial operating system from a TFTP server or local boot device, and then use i.SCSI for data storage once booting from the local device has finishedcitation needed.A separate DHCP server may be configured to assist interfaces equipped with network boot capability to be able to boot over i.SCSI. In this case, the network interface looks for a DHCP server offering a PXE or bootp boot image.This is used to kick off the i.SCSI remote boot process, using the booting network interfaces MAC address to direct the computer to the correct i.SCSI boot targetcitation needed.One can then use a software only approach to load a small boot program which can in turn mount a remote i.
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