> # Information About the SAN Extension Tuner

> The SAN extension tuner (SET) feature is unique to the Cisco MDS 9000 Family of switches. This feature helps you optimize FCIP performance by generating either direct access (magnetic disk) or sequential access (magnetic tape) SCSI I/O commands and directing such traffic to a specific virtual target. Applications such as remote copy and data backup use FCIP over an IP network to connect across geographically distributed SANs. SET is implemented in IPS ports. When enabled, this feature can be used to generate SCSI I/O commands (read and write) to the virtual target based on your configured options.

> Note SAN Extension Tuner is not supported on the Cisco Fabric Switch for HP c-Class BladeSystem, the Cisco Fabric Switch for IBM BladeCenter, and 16-Port Storage Services Node (SSN-16).

> Note As of Cisco MDS SAN-OS Release 3.3(1a), SAN Extension Tuner is supported on the Multiservice Module (MSM) and the Multiservice Modular Switch.

> Applications such as remote copy and data backup use FCIP over an IP network to connect across geographically distributed SANs. To achieve maximum throughput performance across the fabric, you can tune the following configuration parameters:

> - The TCP parameters for the FCIP profile.
> - The number of concurrent SCSI I/Os generated by the application.
> - The transfer size used by the application over an FCIP link.

> SET is implemented in IPS ports. When enabled, this feature can be used to generate SCSI I/O commands (read and write) to the virtual target based on your configured options .

> The SET feature assists with tuning by generating varying SCSI traffic workloads. It also measures throughput and response time per I/ O over an FCIP link.

> Before tuning the SAN fabric, be aware of the following guidelines:

> - Following these implementation details:
> - The tuned configuration is not persistent.
> - The virtual N ports created do not register FC4 features supported with the name server. This is to avoid the hosts in the SAN from discovering these N ports as regular initiators or targets.
> - Login requests from other initiators in the SAN are rejected.
> - The virtual N ports do not implement the entire SCSI suite; it only implements the SCSI read and write commands.
> - Tuner initiators can only communicate with tuner targets.
> - Verify that the Gigabit Ethernet interface is up at the physical layer (GBIC and Cable connected—an IP address is not required).
> - Enable iSCSI on the switch (no other iSCSI configuration is required).
> - Enable the interface (no other iSCSI interface configuration is required)

> See "Creating iSCSI Interfaces" topic for more information.

> - Configure the virtual N ports in a separate VSAN or zone as required by your network.
> - Be aware that a separate VSAN with only virtual N ports is not required, but is recommended as some legacy HBAs may fail if logins to targets are rejected.
> - Do not use same Gigabit Ethernet interface to configure virtual N ports and FCIP links—use different Gigabit Ethernet interfaces. While this is not a requirement, it is recommended as the traffic generated by the virtual N ports may interfere with the performance of the FCIP link.

> This section includes the following topic:

> - Data Pattern

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