[mythtv-users] Mythbackend on VMware Server with DVB-tuners
Raymond Wagner
raymond at wagnerrp.com
Sat Apr 30 19:43:29 UTC 2011
On 30 April 2011 17:20, Tyler T <tylernt at gmail.com
<mailto:tylernt at gmail.com>> wrote:
>
> > > Some say that its overkill to run virtualization at home
> > > I have to disagree
> >
> > No, it's simply overkill.
> > Anything in the userland can be completely isolated from the
> rest of the
>
> Sure it can, but it's a lot easier to use a VM. For example, how many
> users know how to run two parallel installations of Myth on one host
> without them stepping on the other?
>
For FreeBSD, you're a single Google search away from the half dozen
commands needed to build a new world into a directory to run a Jail.
For Gentoo, you follow the same exact stage3 install instructions you
used to set up the system in the first place.
> Plus, a VM is easier to back up and
> restore separately from the rest of your system, can be moved to a
> different host easily, and you never have to worry about an upgrade in
> the VM breaking something on your host OS or in another VM.
>
On my backend, backing up a Jail is as difficult as 'zfs snapshot
zroot/jails/mythbe at date'. Recovery is then either a 'zfs rollback' or
'zfs clone', change in the jail root, and restart of the jail. Unless
you need some special services offered by one kernel or another, there
is no problem migrating from one host to another. A couple years ago
when my firewall died, I took a backup snapshot of my DNS and DHCP
servers, copied it onto another machine, added the necessary aliases,
and I was done. All told it took maybe 5 minutes to bring the new
machine online in its place.
> At work we've saved literally hundreds of thousands of dollars in
> hardware and
> just as much in labor by switching to VMs for 95% of what we do -- VMs
> are here to stay, no doubt about it.
>
You saved hundreds of thousands of dollars in hardware and labor by
switching to isolated containers. The fact that they were full virtual
machines likely made no difference at all.
>
> I have to say, I think it's kind of funny that those of us running
> low-power ARM devices as Myth MBEs are shunned for using "not real"
> hardware and those of us using Atom / VDPAU for FEs are continually
> warned of their "limitations" and are told to buy expensive
> fire-breathing systems instead.
>
As has been explained multiple times, certain backend tasks such as the
scheduler, are time critical. Let them run too long, and you're going
to suffer usability issues and lost recordings. For small installations
with one or two tuners and a handful of channels, an ARM or Atom would
be plenty sufficient. They will not have the power to commercial flag
in a reasonable time frame, will be limited in the physical tuners and
hard drives you can attach, and will not be powerful enough to handle
several tuners and a large channel lineup. Simply put, they are not
one-size-fits-all.
MythTV is a hobby, and the funny thing about hobbies is that they tend
to grow. Users will add tuners, add more frontends, add hard drives,
add larger cable lineups. The ARM and Atom based backends do not have
room to grow, and as such are a very bad recommendation to a new user
feeling things out. For experienced users with limited needs, they're
fine... but then for experienced users with limited needs, they don't
very well need to seek advice from a mailing list.
The recommended machines for frontends would be ones with sufficient CPU
power to handle decoding whatever the user wants in software. Hardware
decoding is a nice bonus, but its capability is statically defined as
what nVidia determined was 'good enough' several years ago. It may not
play your videos because you used encoding options or codecs they chose
not to support. It may not play your videos because of signal
corruption. You may find at some point in the future it does not meet
your needs, and since it is defined statically and cannot be expanded,
your only option is to fall back on software, or failing that because
you bought an Atom, buy new hardware. Again, for experienced users with
known limited needs, they're fine... but it's a bad recommendation to a
new user who doesn't understand the consequences.
While ARMs are a perfectly decent low power systems, MythTV doesn't
support any hardware decoding options they offer. Atoms on the other
hand are simply garbage. They offer similar performance to an ARM, at
several times the power consumption of an ARM, and not all that much
better consumption than more traditional hardware. A homebrew ION
system is going to cost somewhere around $250, and consume 15-20W when
idle. Pre-built systems will be over $300. A mobile Core 2 (such as a
Mac Mini) will be far more expensive, but will actually have lower power
consumption than that ION. On the opposite side of the spectrum, you
can build a desktop i3 for around $300, that runs under 30W idle. For a
dedicated frontend, all you have to do is turn it off when not in use,
and then most of the power consumption argument is moot anyway.
> I'd say anyone running the recommended multi-core, multi-gig,
> multi-spindle Myth system already has so much hardware overkill that
> the tiny overhead of running a VM is a drop in the bucket.
>
Containerization is a perfectly valid and useful ability. It makes
system management much easier when you can isolate different servers,
and prevent their upgrades from impacting other servers and applications
on the same system. Full system virtualization is not such a useful
ability. When you consider server farms often run distros like RHEL and
CentOS which go for years without upgrading the kernel, the ability to
run different kernels is not really that important. How often do you
really need to run both Linux and Windows servers on the same box, and
is it really worth needing people trained to administer both systems of
systems, rather than just more all servers to alternatives that run on
one OS or the other?
Full system virtualization is good for two things, compatibility when
you have no alternative, and for development and testing in a protected
or cross-platform environment. Virtualization took off because it
intrinsically requires containerization, and so was what was available
when administrators began to realize its usefulness. Containerization
is the desirable product, virtualization is just an unnecessary feature
that came along for the ride.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.mythtv.org/pipermail/mythtv-users/attachments/20110430/95edc9ab/attachment.html
More information about the mythtv-users
mailing list