[mythtv-users] ECS LIVA as Backend / Frontend Combo: It Works!

[Dave MythTV]

On Thu, Jan 1, 2015 at 4:49 AM, Mike Perkins <mikep at randomtraveller.org.uk>
wrote:

> On 01/01/15 04:07, Dave MythTV wrote:
>
>> Hey everyone.
>>
>> There are several (three?) threads going now about using the ECS LIVA as a
>> MythTV frontend...  but I'm going to take it a different direction.   :-)
>> I'm here to say that the LIVA also works quite well as a *BACKEND*, and
>> amazingly - as a backend / frontend combo as well !!
>>
>>
>> I'm running Gentoo, so I've been tacking my findings on to SiliconFiend's
>> ECS LIVA How-To thread on the Gentoo forums as I go along:
>> http://forums.gentoo.org/viewtopic-p-7675300.html
>>
>>
>> Short list of my system hardware configuration:
>> -----------------------------------------------------------------
>> ECS LIVA  (BAT-MINI v1.0)
>> $109 model with 32GB eMMC / 2GB RAM   (NO reason to spend more on the 64GB
>> models)
>> 3x older USB ATSC digital tuners with multirec enabled
>> 1.5 TB USB 3.0 2.5" portable (bus powered) hard drive
>> USB MCE-style IR receiver
>> USB RF wireless keyboard/trackpad combo
>> WiFi on the LIVA (no hardwired ethernet)
>> Audio via the analog output
>> 1080P display connected via HDMI
>> USB slim DVD drive
>> -----------------------------------------------------------------
>>
>>  (snip)
>
>>
>>  That seems like a /lot/ of USB peripherals. I understood that box to
> only have two USB ports. How are you connecting your bits? Is there any
> likely contention on the USB bus?
>
> Supplementary question: Is the eMMC card just used for booting, or is it
> used by the OS with r/w access? How is that likely to affect the wear
> rates? As a read-only boot partition I could understand, but r/w seems to
> be asking for trouble.
>
> --
>
> Mike Perkins
>
> _______________________________________________
>
>

It seems like a lot of USB devices, but in use, it doesn't seem to be a
problem.  I have it all connected via a powered 7-port Anker USB 3.0 hub
(which internally is apparently a four port hub with another four port hub
connected to one of the first hub's ports).  The hub itself is connected to
the LIVA's USB 2.0 port, as I had issues with the LIVA's wifi stalling when
running USB 3.0 devices through the hub while on the LIVA's USB 3.0 port.
(See the thread on the Gentoo forums for more details.)   I have the hard
drive connected directly to the LIVA's USB 3.0 port.


If we look from the theoretical side, it looks like it checks out OK.
Wikipedia says that USB 2.0 has a signaling rate of 480 Mbit/s with an
effective throughput of 280 Mbit/s.   The US ATSC broadcast transport
streams are 19.3927 Mbit/s, so that's 58.1781 Mbit/s if all three tuners
are recording.  The IR receiver and the RF keyboard/trackpad receiver are
both USB 1.x devices, so they couldn't use more than 12 Mbit/s tops and
obviously wouldn't need nearly that kind of bandwidth.  But even assuming
they did, we're still only up to 82.1781 Mbit/s.   Assuming the worst case,
of also using the external drive to watch a DVD encoded at the maximum raw
bitrate of 11.08 Mbit/s while everything else is running, our grand total
comes to 93.2581 Mbit/s, which is almost exactly one third of the available
effective bandwidth.   So it appears as though there is *plenty* of
overhead available.  :-)    (Please correct me if any of my figures or
reasoning is incorrect.)


For the eMMC, I'm using it read/write as the system partition, and I'm not
too worried about it.   The eMMC is almost twice as fast as the external
hard drive, so it would seem like a HUGE waste to only use it for booting.
I've taken the first reasonable step to limiting the writes (swap on the
hard drive instead of the eMMC), and the second (tmpfs for portage) isn't
too hard.   If years go by and I've managed to kill the eMMC from too many
write cycles, then I can just pop in a fast USB stick as a replacement, or
replace the entire system with whatever ultra-ultra-ultra-low-power cheap
x86 device has become available by then.    I've found that regular
database backups, copied to a second media (preferably off the machine)
goes a LONG way to easing hardware failure anxiety.   :-)


- Dave
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