HP B6960-90078 manual Changing Block Size on Windows Media Agent, Example

Further Information

Changing Block Size on Windows Media Agent

Changing Block Size on Windows Media Agent

In order to increase the maximum block size on a Windows Media Agent client, you have to modify its Registry. After modifying the Registry, restart the computer. Drivers read MaximumSGList at boot time. The actual formula that a Windows class driver uses to determine the maximum transfer size is:

maximum size = ((number of supported scatter/gather elements - 1)* 4096)

For the typical aic78xx case, it renders the following:

((17-1) * 4096) = 64k (which corresponds to 56k usable data for Data Protector)

	Windows provides a mechanism to support more scatter/gather elements
	via the Registry. Start the regedit32 and add a DWORD value in the
	following Registry key:
	\\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\aic78
	xx\Parameters\Device0\MaximumSGList
	Use the following formula to calculate the value of the MaximumSGList:
	MaximumSGList= ￿BlockSize------------------------- + 1
	4096
Example	The MaximumSGList value for a 256k block size is 65:
	MaximumSGList = (265k/4k) + 1 = 64 + 1 = 65
	If you have, for example, 3 aic78xx based SCSI channels on your system,
	change the appropriate ...	\Device0, ...\Device1 or ...	\Device2 value. If
	you want to set all adapters at the same time, specify MaximumSGList for
	...\Device\.... Omitting the numerical reference sets the value for all
	aic78xx adapters.	￿
	Appendix A		A-51