[mythtv-users] Opinion on a P4 Backend // HDD Throughput

Josh White jaw1959 at gmail.com
Wed Mar 5 20:20:47 UTC 2008


Jeff,

I can't speak to all you listed, but I'm happily running with 5 tuners (2
PVR-500's and 1 PVR-250) on an ancient 2.8GHZ P4, with a 400mhz FSB, and 1GB
of RD RAM. All 5 tuners could can record simultaneously to the 180GB LVM,
which consists of a 120GB ATA 133 disk, and a 60gb ATA133 disk.  The LVM is
formated to XFS.  I have 4 frontends, and they're all connected by 100mbit
CAT6 (I got 200 ft of free CAT6 cable from my work when I set it all up
originally).

Just last night, I put it through its paces fairly hard.  I had it running
such that I was watching a recording in my living room, and my wife was
watching a show live 2 times (in the office and bedroom) and recording it as
well, tying up 3 tuners.  Since she doesn't really understand how this
works, she was watching it 'live' in two different rooms, on two different
frontends, and since it's a show she insists I record, it was being recorded
on another tuner(if she just opened the recording and watched it that way,
she could have watched it in both rooms and recorded it on 1 tuner).  While
this was going on, I was recording two other shows.  Simultaneously, my
machine was commercial flagging two of the recordings (because I limit it to
two jobs).  Also, during this, I just so happen to know that the CPU usage
was about 80%, because I was logged into the machine via VNC, where the
machine was also hosting my Bittorrents (I believe I had 2 torrents going at
the time).

That sure seems like a lot, but it seemed to run smooth and if I hadn't
logged on to do other things, I never would have known how much was going on
from a user perspective.

So from my experience, you should be able to do your SD system with the
hardware you have; and the HD part my require a storage upgrade, but the CPU
will likely be taxed about the same.  I would try using what you have, and
then upgrade anything that doesn't seem satisfactory.


Good Luck,

Josh
On Wed, Mar 5, 2008 at 2:47 PM, Jeff Holicky <myth.myth_user at myth.sent.com>
wrote:

>
> Hi all, I am looking at implementing a Myth system at home - with up to
> five frontends when all is said and done.  We rent a dual tuner PVR and
> also have a cable box - limited to a small harddrive and no real
> archival system nor easy way of playing back multiple formats has helped
> with my decision to create a myth system.  Definitely looking at at
> least 3-4 SD (standard def) tuners initially [PVR 150x4] (later HD) and
> would like some feedback on my initial setup and to realistically set my
> expectations.
>
> Today I want to have the BE act as an occasional FE with plans down the
> road to make it a BE only box (if possible).  Running 100Mbit CAT5 cable
> with the goal to run 1000Mbit CAT6 and/or try wireless.  Perhaps in a
> year or two move to HD by swapping out 2SD tuners.  Start off with two
> dedicated FE's.
>
> Don't want DVD players on each FE - want to stream archive content off a
> NAS device.   (1 or 2TB drive; 100 or Gigabit)
>
> Q1) I am not clear on the ability to do multiple streaming AND recording
> simultaneously.  Someone I spoke to felt my ability to do both may be a
> problem due to bottleneck issues at the HDD.  Assuming a model of 4
> tuners - 1 streaming; 3 recording OR 2 streaming 2 recording; OR 3
> streaming 1 recording -- are all these possible?
>
> Q2) Then there is that "commercial skipping" process - not sure if that
> still needs to be processed off peak times or not.
>
> Q3) Plus is there a difference between
> a) Streaming program A; recording program B
> OR
> b) Recording program A and streaming program A (few minutes offset)
>
> Q4) I have noticed some that already have 2HD and 2SD tuners in one box
> - but then if they are only recording (on one or more), then there may
> not be any problems.
>
> Q5) My friend suggested the issue was less CPU and more HDD - and maybe
> if I was running a 10K drive - MAYBE I would be okay -- and/or if I
> mixed in a RAID system of sorts to balance the load.
>
> Q6) The other thought is adding in a second backend eventually - not
> sure if that is a no brainer or exponentially more complex and not
> desirable.
>
> Q7) I assume playing an archived movie off the NAS is merely networking
> between the NAS and FE - and cabling and less BE - please confirm.
>
> *Config*
> Part of my plan having 4 tuners hit a road block with most MOBOs today
> supporting only 3 PCI cards (Thanks to Brian for pointing that out).  I
> found one so far - but also I remembered I have a P4.  I feel if the P4
> works, based on set expectations, then I can buy a nice higher end
> system as a desktop replacement.  Worse case later turn the P4 into a
> FE.
>
> Currently I have:
> - ASUS P4P800 MOBO (enough PCI slots);
> - Intel P4 2.8Ghz w/HT;
> - 2GB RAM;
> - 450W P/S
> - ATI All-in-Blunder 9600 of which I would only use for controlling the
> video out (if possible)
> - ATA 133 HDD - I have several 120GB 7200RPM drives at my disposal ..
> see below
>
> MOBO supports:
>
> - 2xUDMA 100 (4drives)
> - 2xSATA w/RAID 0
>
> RAID CONTROLLER
> - 2xUDMA 133 (4drives)
> - RAID 0, 1, 0+1, RAID JBOD
>
> Moving to SATA doesn't seem to be that much of an option with this MOBO
> - I figure I am just as well with the RAID controller (I use ATA 133
> today with 4 drives).
>
>
> If my ideas of streaming and recording are not far fetched - but my
> config is a little dated, if possible, please point me in a direction -
> need a MOBO that has X; or a minimum CPU Y etc.
> Just want some input - a "that dog will or won't hunt" big picture
> response.
>
> thanks all & cheers!
> jeff
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