Mailing List Archive

Slave backend storage
I have a scheduling conflict coming up with no obvious way around it.

My first thought was to dig out one of my old USB Hauppauge tuners and make up a new source that
could be used to cover the issue, but then I didn't really want to spend time tampering with the
Master backend and possibly upset something, all for a temporary fix.

So, the next idea was an ad hoc slave backend. I have a spare box I can use - in fact it is an old
master backend box - but the question of what to do with the storage comes up.

I would rather store the video files on the MBE. Since the video directories on the MBE are already
shared over NFS, that would seem the simplest solution. The alternative is local storage, but then
when I decommission the SBE I'd have to move the vidoes; no biggy but the MBE might get confused
when the SBE disappears.

Are there any rules out there how this would work? Problems? Suggestions?

--

Mike Perkins

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Slave backend storage [ In reply to ]
On 21/10/2020 10:32, Mike Perkins wrote:
> I have a scheduling conflict coming up with no obvious way around it.
>
> My first thought was to dig out one of my old USB Hauppauge tuners and
> make up a new source that could be used to cover the issue, but then I
> didn't really want to spend time tampering with the Master backend and
> possibly upset something, all for a temporary fix.
>
> So, the next idea was an ad hoc slave backend. I have a spare box I
> can use - in fact it is an old master backend box - but the question
> of what to do with the storage comes up.
>
> I would rather store the video files on the MBE. Since the video
> directories on the MBE are already shared over NFS, that would seem
> the simplest solution. The alternative is local storage, but then when
> I decommission the SBE I'd have to move the vidoes; no biggy but the
> MBE might get confused when the SBE disappears.
>
> Are there any rules out there how this would work? Problems? Suggestions?
>
There are no problems storing the slaves recordings on a shared folder
on the master backend, If 'Master Backend' override is set they are
directly accessible to the master whether the slave is present or not.
The address must resolve to the same place on both sides. The slave uses
the master's setting for the recording directories.

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Re: Slave backend storage [ In reply to ]
On 10/21/20 5:32 AM, Mike Perkins wrote:
> I have a scheduling conflict coming up with no obvious way around it.
>
> My first thought was to dig out one of my old USB Hauppauge tuners and
> make up a new source that could be used to cover the issue, but then I
> didn't really want to spend time tampering with the Master backend and
> possibly upset something, all for a temporary fix.
>
> So, the next idea was an ad hoc slave backend. I have a spare box I
> can use - in fact it is an old master backend box - but the question
> of what to do with the storage comes up.
>
> I would rather store the video files on the MBE. Since the video
> directories on the MBE are already shared over NFS, that would seem
> the simplest solution. The alternative is local storage, but then when
> I decommission the SBE I'd have to move the vidoes; no biggy but the
> MBE might get confused when the SBE disappears.
>
> Are there any rules out there how this would work? Problems? Suggestions?
>

Having recently done some testing with slave backends, I'd advise
caution.  I didn't have a real reason to build one, but I wanted to test
the use of one. In my case I used a RPI4 as a SBE but I still had to
mess with the Storage Groups on the MBE.  In my case I used the SBE's
own storage for the experiment.

It all worked, but there must be a specific order to decommission the
SGE.  I ended up with a MBE only that was always looking for videos that
had been recorded on the slave backend.  These were test programs that I
didn't care about, but the master back end was always complaining about
them not being found. I'm not good enough at hacking mysql to make that
go away.  Luckily, I did a complete fresh Master backend build when I
switch to Ubuntu 20.04 and MythTV v31 so the problem went away.  But
that could be harsh for some.  Anyway what I did is documented at the
Mythtv Forum:

https://forum.mythtv.org/viewtopic.php?f=46&t=3928


Knowing what I know, which is very little, I'd just add in the USB tuner
into the Master backend. I'm always adding and removing tuners on my
MBE, since my main tuners on the MBE are never touched it has always worked.

One complete independent way of getting this recorded is to use some
small and disposable like a RPI and USB tuner setup as an independent
MBE Combo.  Once the recording is over you could move the recording to
the NAS in the Video Storage group.

Jim A



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Re: Slave backend storage [ In reply to ]
On Wed, 21 Oct 2020 10:32:14 +0100, you wrote:

>I have a scheduling conflict coming up with no obvious way around it.
>
>My first thought was to dig out one of my old USB Hauppauge tuners and make up a new source that
>could be used to cover the issue, but then I didn't really want to spend time tampering with the
>Master backend and possibly upset something, all for a temporary fix.
>
>So, the next idea was an ad hoc slave backend. I have a spare box I can use - in fact it is an old
>master backend box - but the question of what to do with the storage comes up.
>
>I would rather store the video files on the MBE. Since the video directories on the MBE are already
>shared over NFS, that would seem the simplest solution. The alternative is local storage, but then
>when I decommission the SBE I'd have to move the vidoes; no biggy but the MBE might get confused
>when the SBE disappears.
>
>Are there any rules out there how this would work? Problems? Suggestions?

Just adding an ATSC or DVB USB tuner is much less work than a whole
different backend. It is not particularly difficult if it is going to
use the same EPG as you already have. There is no need to add it as a
different source unless it is really different from your existing
sources in some way. You can simply make it the least preferred tuner
for an existing source, by giving it a lower priority and also
specifying it as the last tuner in the scheduling order and live TV
order. If you do that right, then it will only be used for the
recordings that currently cause conflicts.

USB tuners can be a bit temperamental, but I have found it is usually
a problem with the cable. So when setting up a USB tuner, take great
care with the USB cable. Some cables fit loosely into the USB sockets
and cause intermittent failures, especially if the cables get
disturbed or if the PC is in a place where it gets significant
temperature changes. So choose a cable with a slightly larger plug
where possible, so that when you wiggle it in the socket, it does not
move much. And make sure that the USB tuner itself and the aerial
cable it is plugged into are not easily disturbed (cat, vacuuming,
...). A good way to do this is to lay the tuner down on a flat
surface and tape down the cables on either side of the tuner with
parcel tape. This usually requires a slightly longer USB cable
though. And if it is a USB 2.0 device, it is best to use a USB 2.0
socket, if you have one. There have been complications in the past
with some USB 2.0 devices when used in USB 3.0 sockets due to driver
problems. If the USB socket has not been used for a while, it pays to
check for lint or dust in the socket - a squirt of static-free air or
gas from your trusty PC cleaning can is recommended. And if you are
feeling really paranoid, use contact cleaner.
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Re: Slave backend storage [ In reply to ]
On 10/21/20 3:31 AM, John wrote:
>
> On 21/10/2020 10:32, Mike Perkins wrote:
>> I have a scheduling conflict coming up with no obvious way around it.
>>
>> My first thought was to dig out one of my old USB Hauppauge tuners
>> and make up a new source that could be used to cover the issue, but
>> then I didn't really want to spend time tampering with the Master
>> backend and possibly upset something, all for a temporary fix.
>>
>> So, the next idea was an ad hoc slave backend. I have a spare box I
>> can use - in fact it is an old master backend box - but the question
>> of what to do with the storage comes up.
>>
>> I would rather store the video files on the MBE. Since the video
>> directories on the MBE are already shared over NFS, that would seem
>> the simplest solution. The alternative is local storage, but then
>> when I decommission the SBE I'd have to move the vidoes; no biggy but
>> the MBE might get confused when the SBE disappears.
>>
>> Are there any rules out there how this would work? Problems?
>> Suggestions?
>>
> There are no problems storing the slaves recordings on a shared folder
> on the master backend, If 'Master Backend' override is set they are
> directly accessible to the master whether the slave is present or not.
> The address must resolve to the same place on both sides. The slave
> uses the master's setting for the recording directories.
>
We have a slave backend (and RFE) that only gets turned on when there is
a need for it (conflict) and it is configured as Mike describes, with
both machines having the same path to the storage directories, the slave
being through NFS to the MBE.  The MBE doesn't seem to care if the slave
is there or not (although I suspect the mythfrontend startup time on the
MBE may be affected, but it varies hugely due to unknown factors, but
that's another topic).  Our SBE uses a cable box, though, and provides
another "tuner" that can not be simply added to the MBE.  If you have
another tuner, why not just add it and leave it?  (There will be another
conflict some day.)  Or, once configured, that SBE could be like ours;
just turn it on when needed.  What's one more system to support during
upgrades, eh?

Dave D.



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