HP PCIe U320 SCSI Host Bus Adapter - Manual (Page 38)

Increase transfer size
If you are writing to an application that uses a lot of sequential disk I/O to a contiguous area on disk,
you should use as large a transfer size as possible to reduce overhead on the system, on the SCSI bus
and within disk drives.
Analyze your I/Os
For large sequential data transfers, use Direct I/O by selecting FILE_FLAG_WRITE_THROUGH and
FILE_FLAG_NO_BUFFERING
flags with your CreateFile call to avoid the overhead of copying data
from one area of memory to another, to reduce the number of SCSI commands that must be executed,
and to leave system pages available for other data.
If your application requires a small number of I/Os and the transfers are rather small, however, you may
get better performance by letting the system cache your data in the system pages.
You might want to use over-lapped I/O using the FILE_FLAG_OVERLAPPED option with the
CreateFile
call. Overlapped I/O allows the application to send many commands to the device at
once.
38 Troubleshooting