[mythtv-users] Maximum no. of simultaneous recordings in MythTV

agraham agraham at g-b.net
Mon Oct 19 03:04:36 UTC 2009


On 10/19/2009 01:59 AM, drew einhorn wrote:
> On Sun, Oct 18, 2009 at 5:25 PM, agraham<agraham at g-b.net>  wrote:
>> Hi Guys,
>>
>> Does anyone know what the maximum number of simultaneous recordings is in
>> MythTV ?
>>
>> I have 12 DVB-T/S devices, each set for 10 Encoders - MythTV is patched is
>> allow upto 10 virtual encoders per device, this means I have 120 encoders in
>> total (as shown in MythWeb status).
>>
>> When recording 10 things simultaneous, recordings get split in two, i.e.
>> "The X Files" is shown twice ? each file having half the programme.
>>
>> Is there an "simultaneous recordings limit" ? can this be changed ?
>>
>> Thanks in advance.
>>
>> Albert.
>>
>> I'm at (release-0-21-fixes) revision 22528.
>
> Wow, I really don't have a good answer, but I really can't imagine
> keeping that many encoders busy.  In my opinion Bruce Springsteen's
> old song: "57 channels (and nothing on)" is, more often than not,
> pretty close to the mark.  How do you find the time to actually watch
> that much TV?
>
> It sounds like you have a configuration issue, that is your immediate problem.
>
> Once you get past that I expect that even with hardware encoding, your
> system may run out of resources long before you get to 120
> simultaneous recordings.  I'd do some rough calculations on disk
> bandwidth.  How many backends do you have? I'd also look at cpu,
> memory, and network utilization on both front ends and back ends.
> Swapping/paging to disk will kill you on either front ends or back
> ends.
>


I have all this running on a Core i7 (920), with 12G RAM, and 2x1G 
Network, CPU is about 10% when busy. The backend+frontend itself as no 
local storage it, it PXE boots with the OS on AOE disk with 10TB of NFS 
storage.

Remember, DVB-T/S does not require any actual encoding, it's simply 
device I/O. The problem I'm seeing is a MythTV limitation rather than 
system :(

I know it sounds strange, but I record all movies on all channels, all 
the time, for example Yesterday there was 49 Movies on, and about 35 
today, so it's not uncommon to be recording > 10 things at once.


It's almost as if there is some thread limit on the number of record 
threads ?

Albert.











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