[mythtv-users] Virtual Machines, USB tuners and PCI passthrough

Craig Anderson craig.anderson0 at gmail.com
Wed Jul 21 00:10:11 UTC 2010

On 20 July 2010 23:20, Simon Hobson <linux at thehobsons.co.uk> wrote:

> Tyler T wrote:
>  I tried to do PCI passthough in Xen a couple years ago and remember
>> lots of pain, perhaps it's better now ...
> I'm running a backend as a VM with PCI passthrough. I don't seem to
> remember having had any problems with that - and it's not exactly what you'd
> call up to date versions either. I actually do passthrough for two cards -
> one tuner for the Myth backend, and a network card for my firewall/gateway.
>  One more thought: I believe SiliconDust sells a DVB version of the HD
>> HomeRun. If you go that route, a Gig-E NIC in your server should be
>> able to handle 6+ tuners no sweat, and no mucking about with USB
>> drivers.
> However, you may hit another issue with Xen - network performance. AIUI the
> networking in Xen is single threaded, and so if your guests are hard on the
> network then performance can suffer. For that reason, using iSCSI in a guest
> sucks performance wise - but it's OK if you do the iSCSI in Dom0 and pass
> the result block device through as a virtual block device to the DomU.
> As a reference point, I run a single AMD64-2000 processor, 4G ram, a single
> 1.5TB WD Green drive, and a number of guests (mostly fairly lightly loaded).
> I've a single HVR 1110 PCI DVB tuner setup with 3 virtual tuners in MythTV.
> It will happily record two programs while I watch another, it seems to be
> just over the limit to record 3 while I watch one, and it definitely can't
> commflag a recording while recording two and watching another - I rather
> suspect I'm hitting the disk I/O limit of the single drive.
> On the whole, I reckon that you are likely to hit disk I/O limits long
> before you hit the Dom0 network bottleneck.
> At some point I'll be looking to upgrade and I've been thinking about how
> to arrange things. I could just do what I've got now, but with better
> hardware; or I'd considered running Myth on Dom0 and the rest as they are
> now.

Is Xen still the best solution? with RH not supporting it any longer and kvm
seemingly taking over?

Does HD Homerun come in a dvb-t and dvb-s2 varient? I am in a non dvb-c area
of the UK.

Anyone know if kvm or virtualbox (is it a rubbish solution to this problem?)
have the same network issues?

> --
> Simon Hobson
> Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
> author Gladys Hobson. Novels - poetry - short stories - ideal as
> Christmas stocking fillers. Some available as e-books.
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