[mythtv-users] Adding another backend, and moving the master server to it?

David Brodbeck gull at gull.us
Fri Aug 10 18:01:23 UTC 2007


On Aug 10, 2007, at 10:48 AM, Bruce Markey wrote:
> Good. For some reason, people seem to be attracted to the
> idea that it is somehow really cool to have lots of cards
> in one machine. This is not a good objective. Many resources
> come into play so more motherboards, PCI buses, PCI slots,
> disk controllers, disks, CPUs, etc. all help. Adding more
> cards to one host is not very scalable, however you can have
> several machines with two cards or less and avoid resource
> contention issues.

I can vouch for this.  I've found that, with bttv cards at least, the  
safe upper limit for one host is somewhere around four.  More than  
that wasn't stable; I started getting into trouble with dropped  
interrupts.  PCI bus bandwidth can become an issue, too.  This was  
with motion, not mythtv, but since it was a driver issue I suspect  
the limitations are about the same.

Combined frontend/backend systems can be a good way to avoid having  
to put too many cards in one box.  Thanks to Myth's distributed  
design, one master backend with two cards and two frontend/backend  
machines with one card each are just as good as a single backend with  
four cards, from a scheduling standpoint.  If you use a network  
filesystem you can still put all the bulky, noisy disks in the master  
backend.


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