iSCSI

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iSCSI

(Internet Small Computer System Interface) Pronounced "eye-scuzzy," iSCSI is a protocol that enables servers to access remote disks as if they were locally attached. iSCSI "initiator" software in the server converts disk block level reads and writes to SCSI commands that are serialized into IP packets that traverse any local IP network or wide area IP network such as the Internet. At the destination side, the iSCSI packets are decoded by the disk drive array into the appropriate commands for the type of disk drives used (SCSI, Fibre Channel, SAS or SATA). See block level.

Network Management Is Required
iSCSI traffic generally runs in a subnetwork or virtual LAN to keep it separated from the rest of the LAN. To increase the transfer rate, network cards and iSCSI disk arrays may support port aggregation. For example, four Gigabit Ethernet ports could function as one 4 Gbps Ethernet channel, providing approximately a 400 Mbytes/sec data transfer rate.

In addition, iSCSI network switches may be used that are built to optimize the forwarding of iSCSI packets. See IP storage, SCSI, Fibre Channel, SAS and SATA.
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Infrastructure: The iSCSI switch uses an enterprise's existing IP infrastructure including existing Ethernet switches, cabling, GBICs and SFPs.
Storage Devices: The iSCSI switch supports existing legacy storage devices, both FC & SCSI, RAID & JBOD, so there is no need to purchase new storage devices.
Software: The iSCSI switch has both a hardware and a software component.
Human Resources: Because the iSCSI switch operates over the enterprise's existing Internet network, minimal additional knowledge or training is needed to implement or manage the SAN.
An iSCSI switch represents a single integrated hardware/software solution to SAN management, including storage pooling, virtualization, mirroring, striping and remote backup.
In the primary site, a local storage system is attached to the iSCSI switch using either a SCSI or FC connection.
In case of a disk subsystem failure in a primary site, the iSCSI switch directs all read/write operations to the remote mirror partner connected over dark fibre/DWDM.
The example below shows how an SSP (storage service provider) can use the iSCSI switch at a customer site to replicate and protect customer data.
Either way, this is accomplished by having an iSCSI switch in both the primary and recovery sites.
The iSCSI switch high-availability feature monitors the availability of the other site by using the IP network to constantly send and receive heartbeat packets between the two iSCSI switches.
iSCSI Switch IP Take-Over for Enhanced High-Availability
In the event an iSCSI switch is temporarily off-line or becomes overloaded, other iSCSI switches attached to the stone storage and the same host network can take over the IP addresses and data communication for the off-line switch.