30
Troubleshooting
3 Verify that packets are not being dropped along
the LAN/WAN. Many utilities track packet
activity and switch statistics.
Checking 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.
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 using the Ethernet
page in the ATTO ExpressNAV interface.
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.
3 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 applications
Some applications can be configured to change
transfer sizes. Configure the application for the
optimal size for the particular device(s) connected to
the iPBridge.
Checking the host system
The faster the host, the faster your transfer times will
be. 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 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).
Checking 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 cycles on other
operations, thus slowing down performance.
Optimizing ATTO ExpressNAV in Internet Explorer
1 Go to the browser toolbar and select Tools
2Select Internet Options
3 Select the Security tab
4 Select the Custom Level button.
5 On the menu presented, go to the Microsoft
VM, Java permissions and make sure
Disable Java is not selected.
6 Go to the Miscellaneous topic and select
METAREFRESH.