[mythtv-users] Recording/playing back same file via NFS

Brad DerManouelian myth at dermanouelian.com
Mon Aug 13 15:24:12 UTC 2007

On Aug 13, 2007, at 1:23 AM, Billy Macdonald wrote:

> On 8/12/07, Brad DerManouelian <myth at dermanouelian.com> wrote:
>> I know the drive's limits aren't being reached because I can record 1
>> HD + 2 SD recordings and watch HD all at the same time from this one
>> drive as long as the HD program I'm watching is not the one that's
>> recording. Also, this problem happens when recording only 1 SD
>> program locally on the master backend and trying to watch it from the
>> remote frontend.
>> It seems like there's some weird seek latency while reading from and
>> writing to the same file over NFS or while streaming from the master
>> backend. I was hoping for some magic setting that I missed that would
>> improve NFS caching to fix that or whatever.
> This sounds like more of an issue with MySQL and the seek table than
> with NFS or networking.  I don't have a solution for you
> unfortunately, but I would suggest that it's not an issue with your
> network speed.
> The one network issue is does your NFS mount go through the external
> IP?  I notice that the machine name in your fstab resolves to an
> external address for me.  does your frontend resolve that to an
> external address as well?  It should likely go to an internal address.
> Good luck.

I bounced the backend and it started working without issue again. Not  
really a viable solution for when it's recording something I decide  
is important, but at least when it happens next time I know to wait  
until it's done recording and restart the backend to get it working  
again. :)

As far as the network question is concerned, both machines have  
internet-accessible static IP addresses and DNS entries (with  
appropriate security measures), but they are both plugged into the  
same megabit switch. Right now I'm recording SD on the master and SD  
on the slave, plus transcoding two SD programs on the master. I  
started up a file copy from the master to the slave and scp tells me  
I'm getting 22MB/sec and top says this:
Cpu(s): 41.2%us, 13.3%sy, 27.6%ni,  0.0%id,  6.3%wa,  3.3%hi,  8.3% 
si,  0.0%st

I knew there was a reason I put so much money into these boxes. :)

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