PXIe 8262 streaming performance with HDD 8264 on a PXIe 1062Q chassis

Question

Hello,
I have a PXIe 1062Q chassis, running Win XP, with one 8262 connected to an HD8264 and two PXIe 6537 installed, all the three board being on the express slots (3, 4 and 5). Running the benchmark application for testing the streaming speed (Win32FileIO) I get something like 100 MB/s with data chunks of about 4 MB, and around 140 MB/s with chunk of 64 M. How can improve these results toward the theoretical limit off 600 MB/s? Is there any software/driver trick to be applied?
And, in case, which is the best way to exploit the 8262 from C++ written code (using the NI libraries)? Is there anything similar to the Win32FileIO library? I tried using the RAID system from a c++ test program, and the performance seems very poor, while I would need, if not the 600 MB/s rate, at least something around 200 MB/s of continuous streaming.
Thanks in advance,
Piero.
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Answer 1

Hi Neil,
I actually have a 8130 controller, and in fact that was not the problem: I found the problem being the file-caching performed by Windows file system. If you use standard fstream calls from C source code you cannot bypass it, but by using Windows native call (CreateFile(...), WriteFile(...) APIs) and setting the flag for no data caching or buffering inside the call, I managed to get the full bandwith of 600 MBytes/s.
Anyway thanks for the quick reply!
Piero
I'm guessing you have a controller that only
supports x1 PCI Express.  The PXIe-8130 is our highest-bandwidth
controller, with four x4 links going to the chassis.  In the case of
the 1062, each of slots 3, 4 and 5 get a dedicated link from the
controller.  x1 links max out at about 200 MB/s and x4 links max out at
800 MB/s.
So your first step is to use an embedded
controller or use MXI Express x4 instead of x1 back to a host
computer.  While the PXIe-8130 is the best for high-bandwidth data
transfers, the PXIe-8106 should also be sufficient for your needs.
If
you want to stream data to disk from a PXIe-6537, it is already built
into DAQmx.  You simply specify a file name, and the data goes to
disk.  If you want to stream *from* disk, you'll have to do that on
your own.  Here is a C/CVI example for streaming digitizers to disk
using a C API and the Windows File I/O functions.
Neil
Principal Engineer
National Instruments