HP StorageWorks U320e SCSI Host Bus Adapter user guide (AH627-96001, March 2007)

Increase transf

er 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.

Analyz e 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 com m ands 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.

Troubleshooting