[mythtv-users] Disk utilization on slave backend questions

Alex Brekken brekkal at gmail.com
Fri Jul 8 17:13:10 EDT 2005

Thanks everyone, it sounds like I should stick with keeping local
drives in the machines.

One question Bruce about the NFS thing.  Just so I'm understanding
this correctly, I don't need NFS drives in order for my combo
frontend/backend to be able to play a recording which was recorded on
the slave's local drive, correct? (including live TV)
 NFS would only be necessary if I wanted to have the slave WRITE the
recording to a non-local drive...?

In other words, the master backend knows how to get data from the
slave backend without requiring NFS.

Please let me know if I'm mis-understanding this.  Thanks!

On 7/8/05, Bruce Markey <bjm at lvcm.com> wrote:
> Alex Brekken wrote:
> > Hey all, I'm currently running a combo frontend/backend machine which
> > has a 200 GB hard drive, and one PVR-250 tuner card.  I'd like to add
> > a slave backend which would also have a PVR-250 tuner card and a 160
> > GB drive.
> >
> > I feel like I have an OK understanding of how a distributed Myth
> > system will work, but I'm a little confused about the best way to
> > configure the drives.
> >
> > Does it make sense to put the 160 GB drive in the slave backend?  I
> Yes.
> > assume that whatever recording is done on the slave, whether it's live
> > TV or just a standard recording, will get written to that local drive.
> They will be written to the directory on your prefix path set
> in mythtv-setup. If that is a local disk, it will be written
> locally. If the dir is on an NFS mount, the traffic will go
> across the network,
> >  So therefore, if the slave is down for any reason, then I obviously
> > won't be able to watch whatever shows were recorded on it.
> True. but if an NFS mount is unreachable during a recording, the
> recording would fail. I'd rather grumble about having to fix a
> machine before being able to watch a recording than to never have
> the recording succeed in the first place. Network traffic can be
> an issue but reliability is the main reason I use local disks on
> my slaves. Another reason is that files are written contiguously
> when there is only one being written to a filesystem rather than
> fragmented with multiple recordings written to the same disk but
> that's more something for Adrian Monk to worry about.
> > Additionally, can the master backend/frontend machine just "see" the
> > 160G drive on the slave?  Or do I need to set up an NFS or
> > something...?
> NFS or something. Myth doesn't know the fs type, it just writes
> to a directory
> > On the other hand, if I put the 160G drive on the combo
> > frontend/backend box (along-side the 200G drive), then any recording
> > the slave does has to be pushed across the network to the combo
> > machine.  Is this a big deal?
> Depends on the bitrate and network throughput. It will add some
> latency but my not be noticeable. If you have any other apps that
> saturate the net in bursts, you may get damaged recordings. These
> would not be issues with local dedicated drives.
> --  bjm
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