ATTO Technology 2500C operation manual Performance issues, Checking iPBridge Scsi ports

Performance issues

If the host is not getting the performance it should, check the following items.

Checking SCSI devices

1Verify that the devices are running at their highest possible SCSI speed. Refer to SCSI configuration commands on page 47.

Mixing SE and LVD devices on the same SCSI bus forces the speed of the bus to SE, thus slowing faster LVD devices. The iPBridge cannot accelerate an already slow device. Refer to Connecting SCSI devices to SCSI ports on page iii of the Appendix.

2Verify that the proper terminator is being used. An SE terminator forces the SCSI bus to SE speeds.

Checking iPBridge SCSI ports

1Verify that the SCSI port configuration is set to the highest speed using the ATTO ExpressNAV interface or CLI. Refer to SCSI configuration commands on page 47.

The iPBridge SCSI port speed, wide negotiation, and sync negotiation settings all affect the speed of the port. By default, these settings are set for optimal speed.

2Verify that the SCSI devices are equally distributed between the SCSI ports. Refer to Alternative interface options on page 33. Optimal performance is seen when only two high-speed SCSI devices are connected to each SCSI port.

Checking iPBridge Ethernet ports

1Verify that the data ports are set to auto negotiate or forced to 1000 Mbs. Refer to Ethernet Port Configuration on page 23.

2Verify that the MTU size is set to optimal setting for the LAN/WAN environment.

Refer to Ethernet Port Configuration on page 23. The current optimized frame size for the iPBridge is 9k. Smaller frame sizes cause a decrease in performance.

3Verify that the iPBridge TraceLog feature is disabled. Tracelog tracks certain events that occur in the iPBridge. With this log enabled, performance suffers.

Refer to Diagnostic commands on page 43.

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Checking the LAN/WAN

1Verify that the MTU size is set to optimal setting for the LAN/WAN environment. Refer to Ethernet Port Configuration on page 23.

9k frame size is the current optimized frame size for the iPBridge. smaller frame sizes cause a decrease in performance. Many switch and router vendors do not support the larger frame size of 9k or 16k.

2Verify that each associated port in the IP SAN is configured for 1000Mbs.

IP SAN traffic should be segmented so that it does not interfere with the main LAN network traffic.For better performance, the IP SAN should be on its own set of hardware.

3Verify that packets are not being dropped along the LAN/WAN. Many utilities track packet activity and switch statistics.

Checking Ethernet Host Adapter or NIC

Ethernet Storage Adapters generally outperform accelerated NICs and un-accelerated NICs by offloading most of the processing from the host.

An accelerated NIC provides some offloading, but still requires a host OS iSCSI driver, making the host spend more CPU cycles.

An un-accelerated NIC does not offload anything so the CPU must do much of the processing.

To check the Ethernet host adapter or NIC

1Verify that the adapter or NIC is sent to auto- negotiate or forced to 1000 Mbs.

2Set the MTU size to the largest MTU size supported in the LAN/WAN. Refer to Ethernet Port Configuration on page 23.

9k frame size is the current optimized frame size for the iPBridge. smaller frame sizes cause a decrease in performance. Many switch and router vendors do not support the larger frame size of 9k or 16k. Set the maximum transfer size to the most efficient size for the intended target(s). For many tape drives, 64k is the optimal setting.

Checking the applications

Some applications can be configured to change transfer sizes. Configure the application for the optimal size for the particular SCSI device(s) connected to the iPBridge.

ATTO Technology Inc. iPBridge Installation and Operation Manual