[mythtv-users] YARFA - Tricky architectural decisions

Stephen Boddy stephen.boddy at btinternet.com
Sun Feb 27 19:42:18 UTC 2005

Apologies if this is a repost. I submitted ages ago, and I've not seen my 
message appear?!?

Hi List,

YARFA (Yet Another Request For Advice) I'm afraid ;-)

Okay, after months of reading and research, I'm at the crunch time of looking 
to actually buy equipment. Unfortunately, because of my home, I'm struggling 
a bit with exactly what I put where.

First some details: I'm living in a rented flat. No drilling holes in walls, 
floors or ceilings allowed. Both the satellite and terrestrial aerial present 
in the living room. I have a phone point (for ADSL) in the front room and the 
bedroom. The bedroom is close to a second bedroom that I use as an office. At 
the moment my main workstation is in the office along with an IPCop firewall 
box with an extension to the bedroom for ADSL.

Now some requirements:
 * I obviously want to put at minimum an FE (Frontend) in the living room.
 * I want MythWeb (and poss. MythStreamTv) to be available over the net.
 * I want to keep just one box permanently on (*cough* koyoto *cough* ;-)
 * I want to keep the living room as quiet as possible.

Possible architectures:
1. Living room box acts as internet gateway, FE & MBE (Master Backend). I then 
use Wifi to forward the net to my workstation.

        Pros: Simple(r) to build and configure.
                I don't need to worry about dimensioning n boxes correctly.
                Doesn't require "tricks" on MBE.
                Don't have to worry about WOL/nvram/swsusp setup.
                Only needs to send limited traffic (internet) over Wifi.

        Cons: Means additional HD's in living room for storage (Cooling and 
                Lose the nice appliance nature of the IPCop FW. (Security)
                Extra overhead of acting as gateway/FW.
                Living room box always turned on.

2. Living room box acts as FE and SBE (Slave Backend). Office box acts as 
internet gateway (poss w/ IPCop), MBE, and NFS fileserver for SBE. Because 
I'm not convinced about Wifi for coping with up to 3 streams of data bouncing 
around, I'd want to connect with cat5.

        Pros: I can increase storage in the MBE without worrying about space & 
                (I think) I can run IPCop as a Xen domain, keeping that 
"appliance" aspect.
                Keeps the frontend focused on displaying to the user.

        Cons: Much more complex to setup.
                Need to understand where processing power is needed for all 
                Might be unable to use Xen, so still lose "appliance" IPCop.
                WOL/nvram/swsusp can be hit and miss depending on 
                Requires cat5 to be run around under the carpet for reliable 

I don't think I could use Xen on the first architecture, as I'm pretty sure it 
would disrupt the display too much. Whereas using it on the second 
architecture's MBE, it wouldn't be critical because all the data is buffered 
anyway when passing over the network.

The items I still haven't nailed down in my head:
1. Where does the processing for the heavy tasks take place? i.e. transcoding, 
ad-detection etc. We could do with a table like the following in the docs:

function                location                load
live-tv         FE                      high
transcoding             SBE                     high
ad-detection    SBE                     medium
mythweb         MBE                     low

For the second architecture I have an old 400MHz P-II that could handle 
net/db/web. However if the transcoding occurs on the MBE, then it'll be 
permanently bogged down, and the powerful frontend will be sitting idle or 
powered down.

2. Do I have to have a capture card in the _master_ backend, or can I have a 
bare MBE, and only put my tuners in the SBE? The docs seem to imply the MBE 
needs a capture device, but I can't see a reason why they have to be.

If you've gotten this far, well done. I know it was a bit long-winded but the 
usual response to most questions is for more info. I'm giving it out 
up-front ;-)

Now all you have to do is give me an opinion/answers. I was favouring the 
second split architecture, but having put this down on paper, I'm starting to 
lean back to the first single box solution. So, consider me perched on the 
fence with a pained look on my face.

Steve Boddy

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