Avago Technologies LSI20160 - Manual (Page 115)

Performance Tuning for Windows 2000 5-11
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255 or 0xFF. This denotes an absolute maximum transfer size of
1040384, which is 8 Kbytes less than 1 Mbyte (1040384/4K = 0xFE, add
1 for 0xFF or 255).
You must reboot your system for the new registry setting to take effect.
To reset the maximum block size to the default of 64 Kbytes, follow the
instructions above, except use
SYMDFBLK.REG as the data file.
5.4.2 Maximum Number of Concurrent I/Os (Guaranteed)
Windows 2000 only guarantees a maximum of 32 concurrent I/Os active
on a particular SCSI bus. However, due to the method of memory
allocation, the actual limit of concurrent I/Os can vary greatly between
various drivers or versions of drivers. This can have a huge impact on
performance benchmarking between different driver versions or adapter
vendors. In effect, one adapter may actually be able to have 70 or
80 I/Os outstanding, while another adapter could only have 32. This can
also affect systems with high performance storage subsystems, such as
disk arrays.
In order to have a guaranteed number of concurrent I/Os, an entry must
be added to the registry, using the
SYM100IO.REG file.
Important: Be sure to read the information in the SYM100IO.REG data
file before editing it.
Choose one of two methods to add this registry setting:
1. Locate the SYM100IO.REG (supplied with the driver files) using
Windows Explorer and double click on the file.
or
2. Type at the command prompt:
REGEDIT SYM100IO.REG
This inserts an entry in the registry to guarantee a maximum of
100 concurrent I/Os per adapter.
If a maximum other than 100 is desired, the SYM100IO.REG file can be
edited. However, setting this value to a high number uses increasing
amounts of nonpaged pool memory, a critical Windows 2000 resource.
High values for this setting can degrade system performance.