15 ATTO Technology ExpressPCI Ultra/WIDE SCSI Host Adapters Installation and Operation Manual
4 Maximizing Performance with ExpressPCI HBA
If you are getting less performance than you expect, there are several things you can do such as making
sure you are using the latest ATTO driver, setting the registry entry for large block transfers, using ATTO
ExpressRAID for setting up RAID groups, increasing transfer size, and analyzing your system’s I/Os.
While the factory settings on your ExpressPCI
host adapter should provide excellent
performance for a wide range of applications, you
may improve performance by modifying some of
the system factors which affect your ExpressPCI
host adapter.
For example, the ATTO driver can transfer well
over a megabyte with one SCSI command.
NOTE
You must use an ATTO driver when using ATTO
ExpressRAID software.
Use the latest ATTO driver
Determine which drive is currently in use, then
install the latest ATTO driver found at
www.attotech.com.
Windows NT
1
Open
My Computer
2
Open
Control Panel
3
Open
SCSI Adapters
4
Examine the
Driver tab
for your SCSI
adapter. If the driver is not
express.sys
,
install the
express.sys
driver.
5
Either remove the previously-installed
driver or disable it using the Devices applet.
If the system has a built in Symbios or LSI
adapter, do not disable the driver for that
adapter.
Windows 2000 and XP
1
Using the
Device Manager,
select
SCSI &
RAID Controllers
2
Examine the
Driver tab
for your SCSI
adapter. If the driver is not
express.sys
,
install the
express.sys
driver.
3
Either remove the previously-installed
driver or disable it using the Devices applet.
If the system has a built in Symbios or LSI
adapter, do not disable the driver for that
adapter.
Set registry for large block transfers
If your application requires large block transfers,
set the registry entry correctly for the
MaximumSGList keyword. Several files supplied
with the device driver download package can set
this value to any one of the following sizes: 64Kb,
128KB, 256Kb, 512KB, 1MB and NT default
(64KB). The files are ASCII text files and can be
viewed with any suitable editor. The files also
explain the registry setting and how to change the
setting.
The ExpressPCI adapter can have a maximum
transfer size from 64KB to 1MB. If the registry
value is set to a number higher than 0xff, the
driver will reduce the setting to 0xff. The driver
installation process will set the default value to
0xff.
Set up RAID groups with ATTO
ExpressRAID
Instead of using the RAID functionality built into
Windows OS, use the ATTO ExpressRAID
software for the most efficient performance.
ATTO ExpressRAID requires one less level of
driver through which commands must pass and
fewer commands are required to pass through the
driver hierarchy.
Other advantages of ATTO ExpressRAID
striping:
❖
You can boot your system off striped drives
❖
Stripe sets created with ExpressRAID are
recognizable by DOS and Windows
❖
You can stripe removable-media drives with
ExpressRAID.
If you have purchased the striping option,
additional information about ExpressRAID is
