[mythtv-users] small portable DVR

James Abernathy jfabernathy at gmail.com
Mon Jan 14 22:48:58 UTC 2019


> On Jan 14, 2019, at 5:29 PM, Greg Oliver <oliver.greg at gmail.com> wrote:
> 
> On Mon, Jan 14, 2019 at 3:59 PM Jay Harbeston (ISeePeople) <jharbestonus at gmail.com <mailto:jharbestonus at gmail.com>> wrote:
> 
> Backpedaling a bit on what I posted regarding RPi3 ability to record to a USB disk ..
> 
> When I did my testing earlier, I was using a sandisk usb3 128gb memory stick when I was testing the USB port.
> 
> I have since retested using a usb3 seagate hard drive, and looks like I am able to record on the backend RPi from 2 ‘HD’streams and 1 SD stream from one of the HDHR tuners as well as watch an HD stream on a different pi.
> 
> ( In our location, ABC(720p) and CBS(1080i), and CW(480i) are all on one channel) ABC video is around 2.7 Gb per hour, CBS is around 4.0 Gb per hour and CW is just shy of 1 Gb per hour.
> 
> 
> I am surprised that the 128GB USB3 SD memory stick performed so poorly earlier!
> 
> I am going to test using both tuners from the HDHR and try to saturate the capacity coming out of the HDHR.
> 
> Regards,
> 
> Your bottleneck will quickly be that everything shares the same USB bus, so for every packet you get on ethernet, it goes out the other USB port to the disk, so yiou just cut the 244Mbit/s to 122 effectively while they are both in "full" use..  The Pi is never going to be a powerhouse - it is a single chip for the entire board (minus GPU), which is why it is so cheap, but do not try to pull extra horsepower out of it when the horse is already legless :)

Based on what I’ve tested with TVheadend I have 2 HDTV programs recording so that’s 15Mbs *2 from the HDHR and double that for disk writes so we are looking at 60Mbs. The I was watching one of those programs a minute or 2 behind. So that should be another 30Mbs.  So My worse case test so far is 90Mbs.  I think I can push it to 3, but the heatsink may glow red. :-)

> 
>  
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