USB hard drive transfer speed in Labview RT

[gregoryng]

I have a PXIe-8130 running the realtime OS.  I wrote a quick test app that writes a 512 char string (not prepending string size) continuously and outputs the write speed to the front panel.  When I write to U:\test.dat, which is connected to a USB 2.0 hard disk, the write speed is about 1.5 megabytes/sec.  When I write to c:\ni-rt\Labview Data\test.dat, the write speed is about 16 megabytes/sec.

Of course USB will be slower, but 1.5 MB/sec is about USB 1.1 speed,  not USB 2.0 speed.  Is USB 2.0 supported for the realtime OS?  There's no mention of this limitation on the PXIe-8130 specification data sheet, which lists "4 Hi-Speed USB ports."

I'm looking to achieve at least 6 MB/sec on removable storage, which I was expecting the Hi Speed USB ports to support. 

Can anyone comment on these benchmarks?

[Christian Mergl]

When writing a 512 character string I think the overhead of the USB protocal is almost the same size like the data itself.

USB is for streaming, so you will need to create a benchmark who writes a lot of data to get usefull results.

Christian

[gregoryng]

That's a good point. I tried with a 26112 char string, which matches our intended use case.  The USB benchmark in this case is 1.77 MB/sec.

Message Edited by gregoryng on 12-02-2009 05:17 AM

Message Edited by gregoryng on 12-02-2009 05:18 AM