With the advent of iSCSI as the standard for networked storage, businesses can leverage existing skills and network infrastructure to create Ethernet-based SANs that deliver the performance of Fibre Channel—but at a fraction of the cost. iSCSI enables block-level data to be transported between a server and a storage device over an IP network. An iSCSI initiator is hardware or software that runs on a host and initiates I/O to an iSCSI target, which is a storage device (usually, a logical volume) that responds to read/write requests.
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COMPARING iSCSI INITIATOR IMPLEMENTATIONS
There are three basic types of WHAT'S ALL THE BUZZ ABOUT iSCSI? iSCSI initiators: With the advent of iSCSI as the standard for networked storage, businesses can . Software-based iSCSI driver leverage existing skills and network infrastructure to create Ethernet-based SANs thatwith a standard network card. deliver the performance of Fibre Channel-but at a fraction of the cost. iSCSI enables. Software-based iSCSI block-level data to be transported between a server and a storage device over an IPdriver with a network card that network. An iSCSI initiator is hardware or software that runs on a host and initiates I/Oincorporates a TOE to reduce to an iSCSI target, which is a storage device (usually, a logical volume) that respondsthe TCP processing load on to read/write requests.the host's CPU. . Host bus adapter that offloads Upon connection, an iSCSI initiator and iSCSI target authenticate each other. Afterboth TCP and iSCSI processing. login, the target is seen as a local device that can be used like any other SCSI disk.When accessing data, all initiators run at line speed.
CHOICES, CHOICESTo access storage in an iSCSI SAN, a host only needs an iSCSI initiator anda network connection. Initiator implementations differ in price, performance,and flexibility:. Software-based iSCSI driver with a standard network card. All iSCSI andTCP processing occurs in the host's CPU. With this type of initiator, hard-ware costs are minimized.. Software-based iSCSI driver with a network card that incorporates a TCPoffload engine (TOE) to reduce the TCP processing load on the host'sCPU. Currently, this type of initiator is not common, but it will becomemore prevalent over time.. Host bus adapter that offloads both TCP and iSCSI processing. This typeof initiator reduces the TCP and iSCSI processing load on the host's CPUand will be the first to provide boot support. Some iSCSI HBAs can beused for both iSCSI and standard network traffic, while others require aseparate network card for non-iSCSI traffic.
INCREASING HOST CONNECTIVITY TO TARGETSThe same solutions that increase network connectivity on a host provide highly-availableaccess to iSCSI targets. Host connectivity can easily scale upwards using hardwareor software-based methods, including multi-homing, teaming, or multipath I/O. Hostmulti-homing using NIC/TOEs provides some failover and load balancing capabilities.Teaming homogeneous NIC/TOEs provides both failover and load balancing capabili-ties; however, special setup is required. Host-based MPIO iSCSI - THE BEST SAN SOLUTION AVAILABLE TODAYprovides failover and load balancing capabilities and sup- With capabilities for booting and discovery-in addition toports a broad range of network cards and HBAs. An iSCSI data access-the iSCSI protocol represents the most HBA can also use MPIO for failover and load balancing. comprehensive storage protocol available today. All majoroperating systems support iSCSI initiators, providing ACCESSING TARGETS FROM HOSTS businesses with a range of implementations and features.iSCSI is the only storage networking protocol to support With dynamic discovery methods, high performance offloadauthentication, authorization and encryption in the standard. engines, and scalable host connectivity, iSCSI provides The result is security that is well integrated and easy to use. a cost-effective solution for simplifying and managing iSCSI initiators support various methods for connecting to networked storage.iSCSI targets. All initiators support the static procedure, inwhich an administrator manually specifies the full targetiSCSI name and IP address (portal). However, to facilitate "All major operating systems support iSCSI initiators.the connection process, most initiators support discovery, With dynamic discovery methods, high performancewhich is based on the SendTarget command. Using discov- offload engines, and scalable host connectivity, iSCSIery, an administrator specifies just the portal address. Only provides a cost-effective solution for simplifying andtargets authorized for the initiator are returned and made managing networked storage."available for access.
DYNAMICALLY MANAGING TARGETS AND INITIATORSInternet Storage Name Service (iSNS) can be used to facili-tate the discovery, man... [download for more]
