[TangerineSDR] Benchmarking the Odroid N2 with Digital RF

[Phil Erickson]

Hi Bill,

  There is an additional point regarding Digital RF that Ryan mentioned to
me, and I believe to you as well in some earlier discussions.

  The single-threading requirement only holds for each channel
(==directory) of Digital RF data. So if you're dealing with multiple
channels, those could each be written in separate threads with (as required
anyway) separate Digital_rf_write_object instances. So I suggest trying
that as a way to further optimize the writing process, if you haven't
already done so.  Perhaps you could comment?

73
Phil W1PJE

On Mon, Jul 8, 2019 at 11:56 AM Engelke, Bill via TangerineSDR <
tangerinesdr at lists.tapr.org> wrote:

> I received an Odroid N2 4GB model, shipped direct to me from Korea for $94
> (including shipping).  I installed the following:
>
>
>
>    1. Image of Odroid Ubuntu from
>    https://wiki.odroid.com/odroid-n2/os_images/ubuntu
>    2. HDF5 development package: libhdf5- serial dev
>    3. Digital RF from github
>    4. A few other packages necessary to run the above
>
>
>
> BENCHMARKS
>
>
>
> Digital rf comes with some examples; the interesting one for this is the c
> benchmark, which writes out about 1500 M of data using raw binary (to check
> write speed independent of Digital rf); then writes data using Digital RF
> simple, with checksum, and finally with compression.  I tried writing to a
> Western Digital Elements spinning hard drive, and also writing to a ramdisk
> (the 4 GB Odroid has enough RAM than you can create a 2 GB ram disk and
> still have RAM left).
>
>
>
> Values below are all in MB/sec. I tried 3 runs; each gave different
> results, so the values are the average of the 3 runs.
>
>
>
>                       Raw binary write  Digital RF simple  Digital RF with
> checksum    Digital RF with checksum/compression
>
> Western Digital HDD     198.53            187.03
> 116.63                        11.14
>
> Ramdisk                1320.95           1020.58
> 270.72                        11.76
>
>
>
>
>
> TESTING WITH RED PITAYA
>
>
>
> I compiled the John Melton (not to be confused with the 17th century poet John
> Milton <https://en.wikipedia.org/wiki/John_Milton>) program pihpsdr which
> works nicely with the Red Pitaya when it is in HPSDR emulation mode. The
> Red Pitaya runs at 48 ksps, one channel of I & Q, so I duplicate the I & Q
> data across 16 subchannels (8 channels each with 2 antennas), and write it
> out 4 times (4 X 48 = 197) to simulate the planned speed of Tangerine,
> writing out Digital RF.
>
>
>
> The Odroid N2 provides much better results than the Odroid XU4.  It is no
> problem to achieve this data rate writing to ramdisk.  Writing to the
> Western Digital Elements HDD occasionally does miss 6 to 10 buffers, so it
> appears that the HDD writing speed is slightly lower than needed for
> error-free operation. I have discussed this with the MIT Digital RF team;
> the software does not do internal threading (which makes sense because
> formatting and storing this data is a serial operation). My previous tests
> with forking off threads for the writes led to crashes due to Digital RF
> trying to access the same memory in multiple threads (I interpret this to
> mean the Digital RF is not designed as a thread-safe system).  However,
> there are a couple of ways to deal with this:
>
>
>
>    1. Use a solid state drive.  While technically possible, I have found
>    that SDD in the size we need (~ 4 TB) is very expensive (>$800).
>    2. Set up 2 HDDs and write 4 channels to each.  A pair of 2 TB
>    spinning HDs can be had for less than $150. This might be a very practical
>    solution, which I plan to test. Since the N2 has 4 USB-3 ports, you can put
>    2 HDDs on and still have mouse & keyboard connected.
>
>
>
> Another open question is:  how will a cheap spinning HD do, after running
> it in ~ 100% duty cycle for a while?  Probably not well; but remember that
> SSDs are not able to handle an infinite number of read/write cycles either;
> they also have a lifetime.
>
>
>
> -73- AB4EJ
>
> W. D. Engelke (Bill), Asst. Research Engr.
>
> Center for Advanced Public Safety
>
> Cyber Hall
>
> The University of Alabama
>
> Tuscaloosa, AL 35487
>
> Desk: (205) 348-7244
>
> Mobile: (205) 764-3099
>
>
> --
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>


-- 
----
Phil Erickson
phil.erickson at gmail.com
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