Performance Issues; Check Scsi Devices; Check Ipbridge Scsi Ports; Check Ipbridge Ethernet Ports - ATTO Technology iPBridge 2600 Installation And Operation Manual

Performance issues

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

Check SCSI devices

1 Verify that the devices are running at their
highest possible SCSI speed.
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 i of the Appendix.
2 Verify that the proper terminator is being used.
An SE terminator forces the SCSI bus to SE
speeds.

Check iPBridge SCSI ports

1 Verify that the SCSI port configuration is set to
the highest speed using the ATTO ExpressNAV
interface or CLI.
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.
3 Optimal performance is seen when only two
high-speed SCSI devices are connected to
each SCSI port.

Check iPBridge Ethernet ports

1 Verify that the data ports are set to auto
negotiate or forced to 1000 Mb/sec.
2 Verify that the MTU size is set to optimal setting
for the LAN/WAN environment.
The current optimized frame size for the
iPBridge is 9k.
3 Verify that the iPBridge Trace Log feature is
disabled. Refer to
Appendix. The log tracks certain events that
occur in the iPBridge. With this log enabled,
performance suffers.

Check the LAN/WAN

1 Verify that the MTU size is set to optimal setting
for the LAN/WAN environment.
9k frame size is the current optimized frame
size for the iPBridge. Many switch and router
vendors do not support the larger frame size of
TraceLog on page xiv in the
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.

Check 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.
9k frame size is the current optimized frame size for
the iPBridge. 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.

Check 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.

Check the host system

The faster the host, the faster your transfer times are.
The work flow goes only as fast as the slowest
connection in the host system, so transferring data
from an IDE drive, 100Mb connection, a DLT 4000, a
high speed RAID volume across the country, or other
applications, slows the system no matter how fast
everything else is in the system.
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