[mythtv-users] Master back end without tuners, or Xen or ....

[Gareth Glaccum]

I am looking to upgrade, re-install etc. 
I started off thinking I am looking to get a new machine, to replace one of
my current systems. I have two main Myth boxes. I recently had to replace my
backend motherboard and processors after the PSU died, and took the MB and
CPU with it. MB and processor type changed, and I am now having issues. The
disk system did not really change at this point (replaced hardware raid card
exactly).
 
Prior to the change, I had the master backend, and this has the most
storage,  3 DVB-T tuners (USB) and can record 6 streams quite happily. 
A backend and FE combo, with DVB-S can record two streams and play another
HD well.
 
Since having to replace the master backend I have had issues with the
USB-DVB modules failing, and locking out the backend process, specifically
when there is high IO load going on. I think that the motherboard might not
handle high IO well (it is an Intel CPU). 
Once the MBE dies/deadlocks, then no more recordings happen, even on the
working SBE.
 
I am wondering about a couple of choices now for replacing the MBE. One
driver behind the choice, is that I would like the MBE (i.e. the BE that
does the scheduling.) to be separate from the BE that uses the USB modules.
 
I prefer Fedora based systems, if that is going to make much difference to
the answers (I also like prefer to compile the source).
 
One choice would be a Xen setup, NFS storage exported from either dom0 or a
domU. Then the MBE can run (USB can be passed-through?) in a domU. Or even,
I could have 3 domUs and reboot one if one fails.
However, there appeared to be a bit of a downer on Xen in this list?
(looking at gossamer threads). 
 
People suggested that instead of using Xen, it would make sense to use a
chroot environment for process separation. The times and scenarios in which
I read this, it did make sense (someone wanting to keep Samba away from myth
for example). 
However, in my case, I believe that a chroot will not suffice, as the kernel
module crashing will mean that I will need to reboot the server in order to
re-insert the module (unfortunately, stopping the BE doesn't always work
(not even kill -9) and in those times a reboot, or reboot -fn doesn't always
work either). If I can stop the BE, then rmmoding the kernel module,
unplugging the devices, and then re-inserting has only worked once.
 
 
I see three answers, but I only really like the Xen one. Can anyone else
suggest some alternatives?
1)      Separated machines - cons - requires extra machine, more difficult
obtaining 'budget' than replacing/upgrading - requires more power, more
network, and somewhere to put it.
a.       VLP MBE, basically no storage, runs MBE only. Is the processor
capability going to be an issue?
b.      BE with DVB-tuners
c.       BE with DVB-S tuner(s)
2)      Chroot environment - pros - easy setup. Little IO reduction. - cons
- if the kernel module fails, the whole machine might still crash, or need
to be rebooted.
a.       MBE server, has 4 chroot environments, 1 runs MBE without tuner, 4
run separated chroots with 1 DBV-T tuner each. 
b.      BE with DVB-S tuner
3)      Xen setup. - pros - each OS is separated, in theory a kernel module
failure will not result in all machines crashing. - Also updates/upgrades
could be easily managed. - cons - more difficult to set up. Asking wife to
turn machine on and off again is no longer an option
a.       MBE has 4 (or 5) Xen environments. 1 environment has MBE no tuners.
3 domU with MBE and 1 pass-through USB for each dom0
 
 
Better ideas anyone?
Thanks
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.mythtv.org/pipermail/mythtv-users/attachments/20120217/a3f02ddc/attachment.html