how can I DMA the sampled date to harddisk directly?

[yakgg]

hi,

I sampled the data by 5640R. I use the DMA to read the data from the card and then save the data to the harddisk.
I am wondering is there a better way that I can DMA the data to the harddisk directly which can make it faster?

Guang CHEN

[Mauricio Capistran-Garza]

Hi Guang,

There is no way to bypass the host memory when you are DMAing data. That means tha the data must go from the board to RAM to  Hard drive. There are 2 possible bottlenecks in that flow:

1) Hard drive speed: Depending on the IQ Rates that you are using you might need to get a RAID to keep up with the data transfers. Without a RAID you should be able to stream to disk at about 6.25 MS/s (which translates to 25 MB/s).

2) Data processing: Any process that you do to the data before writing it to disk will delay your next read, which can result in an overflow. So, when streaming to disk make sure you are reading binary data.

If you get a RAID and stream binary data you should be able to easily stream 12.5 MS/s and with some work up to 25 MS/s

- Mauricio