[mythtvnz] Hardware Recommendations

[Stephen Worthington]

On Tue, 4 Oct 2011 22:04:16 +1300, you wrote:

>Hi All,
>
>I'm moving towards buiding a dedicated Myth box/home server system and
>am looking for hardware recommendations. It will be a
>front-end-back-end system and I'm also toying with the idea of moving
>my current VPS setup onto it as a KVM virtual machine. There will also
>probably be no end of other uses I can find for it once it's actually
>in place and running.
>
>With all this to consider I'm thinking that the machine will have to be
>fairly beefy. I've been looking at the new AMD Processors (specifically
>the A8-3850 [0]), but I'm not sure whether to go for that or swallow
>the extra cost of an i5. The integrated graphics in the AMD processors
>is of little interest as I'll probably go for an Nvidia card so that I
>can run VDPAU (assuming the integrated graphics can be turned off?).
>
>As I'm going to be running the thing in my living room noise and power
>usage are also concerns, so any tips there will be well received.
>
>I haven't built a PC in a few years, so all recommendations are welcome.
>
>Thanks in advance,
>
>Rob Connolly

CPU fans are much quieter than they used to be, and so are quite a
number of power supplies.  Video card fans can still be a noise
problem, so you should look at the silent Nvidia cards that are
available.  These usually have a heat sink that protrudes into the
next PCIe or PCI slot, so take that into account when planning how
many slots you need.

Take a look at http://www.quietpc.co.nz for some ideas on what is
available (you do not have to buy from there, but almost everything
they sell is intended for making a quiet PC).

The MythTV part of your requirements does not need a particularly
beefy box - recording is really just copying data from the DVB-T
tuners to disk, and for playback it is just copying data to the GPU
and letting the Nvidia chips do all the hard work of H.264 decoding.
The only thing the CPU gets a workout from is scanning the recordings
to find the ads for you (mythcommflag), and that does not work very
well with H.264 anyway, so you may not even want to do that.  You can
set the mythcommflag tasks to be run at low priority in the
background, but they still require a bit more RAM to work with.  A PC
with 512 Mibytes of RAM is fine for recording and playback, and 1
Gibyte of RAM is fine if you want to do mythcommflag on two recordings
at once (on a dual core CPU).  I have 1 Gibyte, and it runs without
problems with no swapper space, although I do have a bit of swapper
space normally in case I want to use the box for other things.  I
often record four or more programs at once and play another back at
the same time.  The CPU also peaks for a second or so whenever the
MythTV scheduler runs to decide how it is going to record things. That
happens whenever a recording is started or stopped, or a new recording
time is defined.  The rest of the time, the CPU is rarely at 100%, and
is often running in a reduced mode.

Since the PC is likely to be on 24/7, it pays to invest a little extra
in a power supply that is more efficient, and efficient over a wider
range.  The total power bill from a 24/7 PC can add up to quite a bit
over a year.  The green lower power hard disks are reported to work
fine with MythTV, and they use significantly less power eg 2-3 Tbyte
drives are 6-7 watts for a green drive and 10 watts for normal or fast
ones.  I can not speak from personal experience on that though, as I
usually buy fast drives.

If you have not built a PC for a while, be aware that hard drives are
rather less reliable these days.  Do not buy any Seagate 7200.11
drives, even if you get them for $1 on TradeMe, as they collapse
without warning.  I have had all but one of mine die, and then the
replacements also die!  The older 7200.10 ones are very reliable, and
the 7200.12 ones are OK - comparable with the other manufacturers. But
it seems that all the home use (cheaper) drives are made now on the
basis that they will have a high failure rate and they will just be
replaced as necessary.  I have had problems with Seagate and Western
Digital drives.  So far I have not had any problems with the Hitachi 3
Tbyte ones, but they are pretty new still.  I have only one Samsung
drive, and that has been good too.  Make sure you install SMART
monitoring software to alert you before a drive finally crashes. The
failure modes I have met recently all showed up on SMART at least a
few days before final death, and I have been able to copy off my data.