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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>Phil,<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>Based on comments from the VLBI / VGOS correlator team at Haystack, I purchased a set of the following disks for my Network Attached Storage device. So far, it has run 24/7 for two years without any problem.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>Hard Disk Drives, HUH728080ALE600 0F23267 8TB 7200 RPM 128MB Cache SATA 6.0Gb/s 3.5" Helium Platform Enterprise<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>Apparently, the Helium reduces “air resistance” inside the drive, making head movement easier and with less wear.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>Rick<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>W2GPS<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'><o:p> </o:p></span></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>From:</span></b><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'> TangerineSDR <tangerinesdr-bounces@lists.tapr.org> <b>On Behalf Of </b>Phil Erickson via TangerineSDR<br><b>Sent:</b> July 8, 2019 2:26 PM<br><b>To:</b> Engelke, Bill <bill.engelke@ua.edu><br><b>Cc:</b> Phil Erickson <phil.erickson@gmail.com>; TAPR TangerineSDR Modular Software Defined Radio <tangerinesdr@lists.tapr.org><br><b>Subject:</b> Re: [TangerineSDR] Benchmarking the Odroid N2 with Digital RF<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal>Hi Bill,<o:p></o:p></p><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal> Agree. One more point: There is no way around the fact that nothing - spinning media, SSDs, etc. - is going to survive repeated writes such as happens in a ring buffer situation. The RAMdisk for the first buffer doesn't solve the problem either - something has to shovel the data out of there onto one of these types of media.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal> The manufacturers still make you pay > 10X per GB for "enterprise class" drives if you want the sustained performance under those stress levels. I can't see any other way around it. The social implications for the personal space weather station need to be thought on some, and a strategy for what will be done needs to be articulated, even if it's "sorry - you'll have to replace media every 2 years". But that conclusion allows for future technology progress to things like magnetoresistive storage, which is supposed to come along Real Soon Now (tm).<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>73<o:p></o:p></p></div><div><p class=MsoNormal>Phil<o:p></o:p></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><div><p class=MsoNormal>On Mon, Jul 8, 2019 at 2:14 PM Engelke, Bill <<a href="mailto:bill.engelke@ua.edu">bill.engelke@ua.edu</a>> wrote:<o:p></o:p></p></div><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in'><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Phil-<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Yes, I’m sure that would work. That would be the technique used to implement my last suggestion (i.e., to write 4 channels to each of 2 separate HDDs), to overcome the speed limitation in the drive(s). I can also code up a test to try writing in 2 write streams (by grouping 4 channels into each) to a single drive (will try tomorrow); on that, my previous experience working with hard drives suggests that this is likely to generate quite a bit of head movement, which detracts from speed – however, some drives are smart enough and quick enough to sort the writes in their buffer and write them in the lowest latency order… so your mileage may differ… I’ll publish the results of that test when I complete it.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>-thanks & 73- Bill<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b>From:</b> Phil Erickson <<a href="mailto:phil.erickson@gmail.com" target="_blank">phil.erickson@gmail.com</a>> <br><b>Sent:</b> Monday, July 8, 2019 11:57 AM<br><b>To:</b> TAPR TangerineSDR Modular Software Defined Radio <<a href="mailto:tangerinesdr@lists.tapr.org" target="_blank">tangerinesdr@lists.tapr.org</a>><br><b>Cc:</b> Engelke, Bill <<a href="mailto:bill.engelke@ua.edu" target="_blank">bill.engelke@ua.edu</a>><br><b>Subject:</b> Re: [TangerineSDR] Benchmarking the Odroid N2 with Digital RF<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Hi Bill,<o:p></o:p></p><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> There is an additional point regarding Digital RF that Ryan mentioned to me, and I believe to you as well in some earlier discussions.<o:p></o:p></p></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p></div><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> 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?<o:p></o:p></p></div></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>73<o:p></o:p></p></div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Phil W1PJE<o:p></o:p></p></div></div></div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>On Mon, Jul 8, 2019 at 11:56 AM Engelke, Bill via TangerineSDR <<a href="mailto:tangerinesdr@lists.tapr.org" target="_blank">tangerinesdr@lists.tapr.org</a>> wrote:<o:p></o:p></p></div><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-top:5.0pt;margin-right:0in;margin-bottom:5.0pt'><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>I received an Odroid N2 4GB model, shipped direct to me from Korea for $94 (including shipping). I installed the following:<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><ol start=1 type=1><li class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l0 level1 lfo1'>Image of Odroid Ubuntu from <a href="https://wiki.odroid.com/odroid-n2/os_images/ubuntu" target="_blank">https://wiki.odroid.com/odroid-n2/os_images/ubuntu</a><o:p></o:p></li><li class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l0 level1 lfo1'>HDF5 development package: libhdf5- serial dev<o:p></o:p></li><li class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l0 level1 lfo1'>Digital RF from github<o:p></o:p></li><li class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l0 level1 lfo1'>A few other packages necessary to run the above<o:p></o:p></li></ol><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>BENCHMARKS<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>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).<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>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.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:10.0pt;font-family:"Courier New"'> Raw binary write Digital RF simple Digital RF with checksum Digital RF with checksum/compression</span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:10.0pt;font-family:"Courier New"'>Western Digital HDD 198.53 187.03 116.63 11.14</span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:10.0pt;font-family:"Courier New"'>Ramdisk 1320.95 1020.58 270.72 11.76</span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:10.0pt;font-family:"Courier New"'> </span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:10.0pt;font-family:"Courier New"'> </span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>TESTING WITH RED PITAYA<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>I compiled the John Melton (not to be confused with the 17<sup>th</sup> century poet <a href="https://en.wikipedia.org/wiki/John_Milton" target="_blank">John Milton</a>) 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. <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>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:<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><ol start=1 type=1><li class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l1 level1 lfo2'>Use a solid state drive. While technically possible, I have found that SDD in the size we need (~ 4 TB) is very expensive (>$800).<o:p></o:p></li><li class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l1 level1 lfo2'>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.<o:p></o:p></li></ol><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>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.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>-73- AB4EJ<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>W. D. Engelke (Bill), Asst. Research Engr.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Center for Advanced Public Safety<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Cyber Hall<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>The University of Alabama<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Tuscaloosa, AL 35487<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Desk: (205) 348-7244<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Mobile: (205) 764-3099<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p></div></div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>-- <br>TangerineSDR mailing list<br><a href="mailto:TangerineSDR@lists.tapr.org" target="_blank">TangerineSDR@lists.tapr.org</a><br><a href="http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org" target="_blank">http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org</a><o:p></o:p></p></blockquote></div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><br clear=all><o:p></o:p></p><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p></div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>-- <o:p></o:p></p><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>----<br>Phil Erickson<br><a href="mailto:phil.erickson@gmail.com" target="_blank">phil.erickson@gmail.com</a><o:p></o:p></p></div></div></div></blockquote></div><p class=MsoNormal><br clear=all><o:p></o:p></p><div><p class=MsoNormal><o:p> </o:p></p></div><p class=MsoNormal>-- <o:p></o:p></p><div><p class=MsoNormal>----<br>Phil Erickson<br><a href="mailto:phil.erickson@gmail.com" target="_blank">phil.erickson@gmail.com</a><o:p></o:p></p></div></div></body></html>