Information Storage Management Certification question Library FAQ Series 18

 

Work:

Iscsi host connectivity requires a hardware component, such as a NIC with a software component (iSCSI initiator) or an iSCSI HBA. in order to use the iSCSI protocol, a software initiator or a translator must be installed to route the SCSI commands to the TCP/IP stack.

A standard Nic, a TCP/IP Offload Engine (toe) Nic card, and an iSCSI HbA are the three physical iSCSI connectivity options.

A standard Nic is the simplest and least expensive connectivity option. it is easy to implement because most servers come with at least one, and in our cases two, embedded tables. it requires only a software initiator for iSCSI functionality. however, the NIC provides no external processing power, which places additional overhead on the host CPU because it is required to perform all the TCP/IP and iSCSI processing.

If a standard Nic is used in heavy I/O load situations, the host CPU may become a bottleneck.

Toe Nic help alleviate this burden. A toe Nic offloads the TCP management functions from the host and leaves iSCSI functionality to the host processor. the host passes the iSCSI information to the toe card and the toe card sends the information to the destination using TCP/IP. although this solution improves performance, the iSCSI functionality is still handled by a software initiator, requiring host CPU cycles.

An iSCSI HbA is capable of providing performance benefits, as It offloads the entire iSCSI and TCP/IP protocol stack from the host processor. use of an iSCSI HbA is also the simplest way for implementing a boot from San environment via iSCSI. if there is no iSCSI HbA, modifications have to be made to the basic operating system to boot a host from the storage devices because the NIC needs to obtain an IP address before the operating system loads. the functionality of an iSCSI HbA is very similar to the functionality of an FC HbA, but it is the most expensive option.

A fault-tolerant host connectivity solution can be implemented using host-based multipathing software (e.g ., EMC powerpath) regardless of the type of physical connectivity. multiple routing can also be combined via link aggregation technologies to provide failover or load balancing. complex solutions may also include the use of vendor-specific storage-array software that enables the iSCSI host to connect to multiple ports on the array with multiple volumes or hbas.

 

HbA

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Host bus adapter (HBA) hardware that connects a host computer to a storage area network or directly to a storage device.

I/O devices enable sending and logging ing data to and from a host. This com-munication may be one of the following types:

• User to host communications

• Host to host communications

• Host to storage device communications

Handled by a host bus adaptor (HBA ). hbA is an application-specific integrated circuit (ASIC) Board that performs I/O interface functions between the host and the storage, relieving the CPU from additional I/O processing workload. hbas also provide connectivity outlets known as portsto connect the host to the storage device. A host may have multiple hbas.

 

Fcip

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Today, Internet Protocol (IP) has become an option to interconnect geographically separated sans. two popular protocols that extend block-level access to applications over IP are iSCSI and fiber channel over IP (fcip ).

Fcip uses a pair of bridges (fcip gateways) communicating over TCP/IP as the transport protocol. fcip is used to extend FC networks over distances and/or an existing IP-based infrastructure, as specified strated in Figure 8-2 (B ).

Today, iSCSI is widely adopted for connecting servers to storage because it is relatively inexpensive and easy to implement, especially in environments where an fc san does not exist. fcip is extensively used in disaster-recovery implementations, where data is duplicated on disk or tape to an alternate site.

Fcip is a tunneling protocol that enables distributed FC San islands to be transparently interconnected over existing IP-based local, metropolitan, and wide-area networks.

 

Converged network adapter

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Converged network adapter (CNA)-a technology that supports data networking (TCP/IP) and Storage Networking (Fiber Channel) traffic on a single I/O adapter.

The key fcoe components are:

• Converged network adapter (CNA)

• Cables

• Fcoe Switches

Converged network adapter

A CNA provides the functionality of both a standard Nic and an FC HbA in a single adapter and has lidates both types of traffic.

CNA eliminates the need to deploy separate adapters and cables for FC and Ethernet communications, thereby cing the required number of server slots and switch ports.

CNA offloads the fcoe protocol processing task from the server, thereby freeing the server CPU resources for application processing. a CNA contains separate modules for 10 Gigabit Ethernet, fiber channel, and fcoe Application Specific Integrated Circuits (ASICs ). the fcoe ASIC encapsulates FC frames into Ethernet frames. one end of this ASIC is connected to 10gbe and FC ASICs for server connectivity, while the other end provides a 10gbe interface to connect to an fcoe switch.

 

 

Answer:

D-converged network adapter