Why does the PXI slow down when I acquire huge amounts of data

[kasula]

Hello,

   We are using PXI 1042Q chassis with PXI RT-8106 microcontroller. I am acquiring data using producer consumer loop. Basically during the starting stage when I have very few files that are acquired the labview program is operating fast enough. But as the number of files increases the labview seems to be slowing down, which is a strange thing I believe. Lets say I have each file of 8MB size. And if I have 1000 files of such size, the process is slowing down drastically. Is there any wayto get around this problem. I know that by transferring these files to flash drive or hard disk and deleting from PXI would helpin speeding up the process. 

Thanks,

kartik

[Peñata]

Hi kasula,

I just want to make sure I understand your problem. You are acquiring data on your PXI-8106 and writing this data to multiple files, approximately 8MB each. Are you writing the data to one file and then writing to another file and then another and so on and so forth? Or are you writing to many files at the same time? What kind of files are you writing to (binary, text, TDMS)?

Thank you for choosing National Instruments.

Aaron Pena

National Instruments

Applications Engineer

http://www.ni.com/support

[kasula]

Hi,

   I am writing to multiple binary files not at the same time but one file after another. basically I am storing the data in the memory provided on the PXI unit (8106RT).

[Peñata]

Hi kasula,

In the memory or on the hard drive?

Thank you for choosing National Instruments.

Aaron Pena

National Instruments

Applications Engineer

http://www.ni.com/support

[kasula]

Hi,

    I am storing in to the harddrive.

Thanks,

kartik

Message Edited by kasula on 10-30-2009 07:44 AM

[Peñata]

Hi kasula,

A few more questions about your application:

1.) Are you running this as a startup executable on the controller or are you running this from the LabVIEW environment on your development machine?

2.) How are you ending one file when it has reached it's size and open a new one for writing?

3.) How are you seeing your application slow down?

Thank you for choosing National Instruments.

Aaron Pena

National Instruments

Applications Engineer

http://www.ni.com/support 

[kasula]

Hi,

1) I am running this from the Labview environment on my development machine. I am connected to PXI through ethernet cable.

2) Actually I specify the number of seconds of data to acquire. I perform the following steps to acquire the data.

    a) Open a file using Open/create/Replace file.vi

    b) Store the data in to the file

    c) Close the file using Close.vi

3) In our application we have written program such that we switch through sensor sets and apply voltage and record data. Initially this application was taking lets say 3 minutes to finish switch and collect data.

    After acquiring huge amount of data its taking like 10 minutes to complete the same process.

Thanks,

kartik

[Peñata]

Hi kartik,

I just wanted to clarify a couple things. Are you creating brand new files and writing ~8MB of data to each file and then closing the reference to the file? Or are you appending to already existing files? Can you be a little more detailed about your application, particularly the loop or section of code where you are writing to your file? What else is going on in that loop? If you could post a screenshot of that part of the code, it could be helpful.

Thank you for choosing National Instruments.

Aaron Pena

National Instruments

Applications Engineer

http://www.ni.com/support