ATTO Technology 2500C - Manual (Page 40)

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ATTO Technology Inc. iPBridge Installation and Operation Manual
Performance issues
If the host is not getting the performance it should,
check the following items.
Checking SCSI devices
1 Verify 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.
2 Verify that the proper terminator is being used.
An SE terminator forces the SCSI bus to SE
speeds.
Checking iPBridge SCSI ports
1 Verify 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.
2 Verify 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
1 Verify that the data ports are set to auto
negotiate or forced to 1000 Mbs. Refer to
Ethernet Port Configuration on page 23.
2 Verify 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.
3 Verify 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.
Checking the LAN/WAN
1 Verify 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.
2 Verify 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.
3 Verify 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
1 Verify that the adapter or NIC is sent to auto-
negotiate or forced to 1000 Mbs.
2 Set 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.