[mythtv-users] Disk utilization on slave backend questions

Alex Brekken brekkal at gmail.com
Sat Jul 9 18:00:37 EDT 2005

Chad, so what you're saying is that if you want to listen to music it
needs to be stored on an NFS mount (unless it's on a local disk)?  So
in other words, if I have a master-backend machine that sits in the
basement with all the tuner cards and storage, and then a lightweight
frontend in my living room, if I want to listen to music through that
frontend the music needs to be sitting on an NFS mount in the backend?

On 7/9/05, Chad <masterclc at gmail.com> wrote:
> > Correct. Playback can go over a socket between a backend and
> > frontend but there is no socket for one backend to send data
> > to another backend to write the file (nor should there be).
> > Mythbackend just needs a path to a writable directory.
> >
> > > In other words, the master backend knows how to get data from the
> > > slave backend without requiring NFS.
> >
> > Master and slaves don't actually send recording data file content
> > between each other. It is when a frontend wants to do playback
> > that the magic happens. Say you have master "A" slave "B" and
> > slave "C" each with local disks. You sit at host "C" watching
> > the frontend and you select a show that happens to have been
> > recorded on "B". The frontend asks the master 'hey, where can
> > I find this file?' The master says it is on "B". The frontend
> > on C then opens a socket to the backend on B who starts sending
> > the data. These two myth processes negotiate a "read ahead buffer"
> > that sends data ASAP while playback is going on until it gets
> > two MB ahead.
> >
> > Next let's say you pick a show that was recorded on "C". You
> > would think it would go through the same steps again to connect
> > to the local backend. However, the frontend cheats. It first looks
> > to see if there is a prefix directory setting for it's hostname.
> > If so, it checks to see if the file is there and will open the
> > local file without going through any backend (this is a good thing).
> >
> > Because the frontend can read a local file or do smart application
> > specific buffering for remote files, you don't need NFS for
> > playback.
> >
> > --  bjm
> > _______________________________________________
> Wow, nice explaination!
> I just wanted to chime in and say that one does need NFS mounts IF
> they are using mythvideo/mythmusic.  I chose a central location for
> these files, and they are a subdir of my existing MythTV recordings
> directory, which is universally /mnt/MythTV.  So, on my MBE I create a
> directory /mnt/MythTV/videos and NFS export ONLY this directory to the
> frontends.  That way the recordings are still held locally in
> /mnt/MythTV, but the NFS mount directory /mnt/MythTV/videos is
> seamless.
> Chad
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