Re: [Discuss-gnuradio] UHD USRP Source for B2x0 overflows File Sink

[Marcus D. Leech]

On 05/09/2015 09:02 AM, Murphy, John wrote:
> Marcus et al,
>
> Had to drop this to do some work on another project yesterday, but
> still want to pursue this just a little further if you don't mind,
> because the numbers you are giving all look to me like it should be
> able to be made to work.
>
> You found my SDD sequential sustained write speed of 69 MBytes/sec.
> If I attempt to save data at 14 MSamp/sec to disk with complex 16-bit
> integers I believe there is an average long-term rate of 56 MBytes/sec
> going to the disk.
>
> So I am not understanding - it seems to me like I have plenty of
> sustained throughput overhead to make this work, with the right
> buffering to take up the temporary slack.
>
> With 16 GBytes of RAM (the system is using some, but still) I would
> expect that I can buffer up something like 4 minutes of data at the
> required 56 MBytes/sec rate - seems like with the proper setup there
> should be plenty of capability to ride through whatever other kernel
> operations etc are momentarily stalling the disk writes.
>
> Thanks, I appreciate you taking the time and list bandwidth to help me
> understand this,
> - John
You could try a simple experiment that tests your disk subsystem write 
performance without SDR stuff at all.  Something like:

time dd if=/dev/zero of=some-file-on-your-disk bs=2000000 count=15000

This should write a 30GB file.   The 'time' command will report how long 
it took.  Then it's just a simple matter of math to figure out what your 
achievable long-term write rate is.