Increase speed of file writing (disbabling caching?)

[frau]

I am already writing in sections of 1048576 Bytes so I don't think that is the issue. How would you open the file and set the file size to a certain size? (I'm only a month into using LabVIEW, working as a student in my gap year between school and uni).

[TCPlomp]

There is a function 'Set File Size' (and you could easily calculate the exact size beforehand).

 N*RMM Block Size*Blocks Read per loop*Valuesize (I guess 4).

 

Ton

[frau]

I had just found that function, I really should've checked first! It is very easy to calculate the file size, simply the requested number of "blocks to read" * RMM Block Size. It does increase the speed of writing, but when the function is asked for data that it has not already read it seems to slow right down again to only 1MByte/s.

The data is stored on a RAID in a series of sequentially named 100MB files, could this be causing any of these difficulties? For the final project the data will be on one Removable Memory Module, sequentially placed, and accessed through a fibre-channel card.

[TCPlomp]

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frau wrote:

...but when the function is asked for data that it has not already read it seems to slow right down again to only 1MByte/s.

...

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So now we are talking about the speed of the DLL function?

Could you show a the piece of code as it currently is?

Ton

[frau]

I suspect it could well be the speed of the dll function that is slowing this function down, but it should read data fairly fast, it is written in C++, has minimal processing to access the correct data and then uses fstream to read the data out.

The attached print screens are the two main cases that will execute, the false structure executes when the requested number of blocks is not a multiple of the maximum number of blocks that are read per loop.