Aa 4000 Software Architecture - HP NetServer AA 4000 Reference Manual

HP NetServer AA

AA 4000 Software Architecture

3-2
The main value of the HP AA 4000 software is its ability to "split"
the Windows NT architecture and allow the IOPs to function as the
I/O agents of the CEs. Looking at the array as a whole and the
Windows NT architecture, what is in effect happening is the CEs are
operating in User mode and the IOPs are operating in Kernel mode.
However, the reality is the CEs are running one synchronized copy
of Windows NT and its I/O traffic is that of the Marathon Interface
Card. The IOPs are each running their own copy of Windows NT
and spending most of the time servicing the I/O requests that come
through the MIC. For disks, this is divided up between disk.sys
running on the CEs and scsiport.sys along with the device drivers are
running on the IOPs. For the network, the NDIS on the CEs ends up
with its I/O on the NDIS of the IOPs. All device drivers operate on
the IOPs.
There are five key areas in the software architecture:
•
I/O Redirector – In the CE's, for each supported device, the
redirector intercepts I/O requests in the CE and moves them to
the IOPs through the Marathon Transport.
•
I/O Provider – On the IOPs, this counterpart to the CE's
redirector receives requests from the CEs through the Marathon
Transport and sends them to the Windows NT device drivers
local to the IOP. The providers also handle incoming I/O
(networking) and pass it to the CE redirectors through the same
Marathon Transport.
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