ATTO Technology 1550D - Manual (Page 25)

21
ATTO Technology Inc. iPBridge Installation and Operation Manual
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 the 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 Mb.
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. 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.
1
Verify that the iSCSI storage adapter or NIC is
connected to the fastest PCI bus connector
supported by the adapter or NIC.
If the adapter supports PCI-X, place the
adapter in a PCI-X slot. If one is not available,
the host might not achieve the optimal
performance capable from the adapter.
Even placing a PCI-X adapter into a 64 bit 66
MHz slot loses performance. Some adapters
adjust clock speed depending on the speed of
the PCI slot into which they are plugged.
2 The host OS disk and swap disk/partition/file
should be on a high speed drive such as a SCSI
drive to minimize the time needed to access the
host’s virtual memory.
The more memory a system has, the less time
it spends accessing virtual memory (hard drive
space).
Check the Operating System
If possible, eliminate swap space and virtual drives
which require large amounts of system memory.
However, the OS might not allow the elimination of
swap space. An OS set to run many kinds of different
servers spends much of its CPU cycle on other
operations, thus slowing down performance.
Use the ATTO iSCSI performance
configuration tool (Windows only)
The ATTO iSCSI performance configuration tool
changes the Windows registry parameters for
Microsoft iSCSI Initiator and TCP/IP to enhance
overall data throughput.
1
From the CD which came with your iPBridge,
copy the Perftune.exe file to your hard drive.
2 Execute the program.
3 Click on Use ATTO Performance Settings.
Settings take effect on the next system reboot.
The following settings are affected:
FirstBurstLength
The maximum amount, in bytes, of unsolicited data an
iSCSI initiator may send to the target during the execution
of a single SCSI command including the immediate data
and the sequence of unsolicited Data-Out PDUs which
follow the command. FirstBurstLength cannot exceed
MaxBurstLength
ATTO value: 1048576 decimal 00100000 hex