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use Reliance or FAT32 for PXI Realtime

when i tried to format the hard disk on a pxi system, it offered two choices: Reliance (NI Recommanded) and FAT.  What's the advantage of Reliance over FAT32?  besides the 'no data loss during power off'. 


Our application generates hundreds of hundreds of files (some tiems 500+ files in a single directory, with file sizes varing from 1MB to 50MB).  Can the Reliance file system handles this kind of usage without much performance hit?  and how about file fragmentation?





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The Reliance filesystem is a transactional filesystem.

Its advantages are load-balancing, speed, porting ease and data preservation in the event of a powerdown.

It supports disk sizes up to 2 terabytes, file sizes up to 4 gigabytes, and a wide range of block sizes.




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thanks for the reply. do you think the Reliance format is suitable for high-disk-write applications?


in our system, the application will generates hundres of files every hour, file size could be from 500KB to 50MB.  once the files are generated, they will be downloaded by a host application, the pxi controller still keeps a local copy of the files for a number of days.


we are not that much concerned about the data loss during powerdown, but the drive performance really matters.  we have been using FAT32 in the past, but this has resulted in file fragmentation over time and affected system performance overall. How does the Reliance handles the file fragmentation?



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Even when using the reliance file system it is important to intelligently group files across multiple directories to keep the number of files per directory low. See here.

It is more important to write data as multiples of the sector size of your drive since every read and write operation executes in this minumum size.

You can determine the sector size with the Get Volume See also: Optimizing File I/O in LabVIEW and LabVIEW RT





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Thanks for your advice.



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Hello All,


Is there any way I can get the PXI RT controller to save files larger than the 4GB limit? The file I need to store is 50GB. Suggestions will be appreciated. Thanks!





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Hi Aditya - in the future, it is best to create new forum threads for new questions to make the database searchable.


I have not been able to find away to increase the file size for reliance systems. You could try FAT32 but that system is not fault safe and has potential to corrupt the disk if power is lost during IO. This could be a pretty big risk when writing such large files.


We highly recommend decreasing your file size to be under 4 GB. This helps prevent corruption and makes your program more manageable. Please see the Best Practices for Target File IO with LabVIEW Real-Time document.

Applications Engineer
National Instruments
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Message 7 of 8

Hello again,

Thanks for your response. I can write to different files, keeping each less than 4GB -- and then concatenate them offline. Thanks again!





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