Is it possible to make transfer larger then 64KB via SCSI Pass-Through?

If so how is the best way to go about it?

If this is SCSI HBA dependent how can you tell the maximum transfer length
size allowed?

I looking to test up to 16MB transfers.

PORT_CONFIGURATION_INFORMATION::MaximumTransferLen gth

"S. Heck" <SHeck@discussions.microsoft.com> wrote in message
news:3B028156-B6DC-434C-9D28-0F9F794E09A1@microsoft.com...

Thank you for this information.

Is there a limit on the OS side (Windows 2003)?

Thanks!

"Z. Yang" wrote:

Typically the maximum that can be described by an MDL -- ~64Meg

--
The personal opinion of
Gary G. Little

"S. Heck" <SHeck@discussions.microsoft.com> wrote in message
news:B44913C1-54A2-4DA8-8C9A-88F0C217041A@microsoft.com...

That's not the correct value (or rather not the most important parameter).
First, you need to set MaximumSGList in the driver's service key
(HKEY_LOCAL_MACHINE->SYSTEM->Current Control Set->Services->{vendor device
name}->Parameters->Device) in order to support larger transfers. The
supported range of values for this parameter is 17-255 which represents
pages, so you can do a 255*4K transfer (if aligned, which passthroughs must
be).

http://msdn.microsoft.com/library/de...dbeeb0.xml.asp
(says 16-255, but 16 will not allow a 64k unaligned transfer)

The HBA may not support the maximum. In that case, the driver for the
adapter has the option of decreasing this by adjusting
PORT_CONFIGURATION_INFORMATION.NumberOfPhysicalBre aks (as well as
MaximumTransferLength).

http://msdn.microsoft.com/library/de...asp?frame=true

[It is possible that not enough contiguous memory is available when the
driver loads to support the maximum transfers (depends on how much is
requested by the miniport) and a driver can fail to load. This is more
likely on a driver update or with a lot of adapters.]

"Gary G. Little" <gary.g.little@seagate.com> wrote in message
news:44107a7c$0$3282$6d36acad@taz.nntpserver.com.. .