[mythtv-users] Dual Core or Dual CPU??

[Michael T. Dean]

On 08/04/2007 09:51 AM, Brian Wood wrote:
> On Saturday 04 August 2007 07:29, GyroTech wrote:
>   
>> I was looking at forking out for a dual Opteron setup, but since these
>> Core 2 Duos have come out they seem to be able to handle a fair grunt.
>> So, has anyone worked with either\both setups care to give me an honest
>> opinion on what they would do. Obviously the Intel chips and lower power
>>     

This one may not be so true...  I'll agree that Intel has said so and
that many sites have said so, but there is some dissension among the
ranks (and the testing procedures have been called into question).  But,
as someone recently said, the /best/ way to truly save power is to shut
down the machine when it's not needed.

>> and price on their side,

Perhaps--I haven't looked at prices and wouldn't be surprised if that's
the case.  However, I will say that Core 2/Core 2 Duo is a better
architecture than Athlon X2/Opteron (while Core or Core Duo is an OK
architecture that's not better than the Athlon X2/Opteron
architecture).  So if CPU performance were an issue...  (keep reading)

>>  but Opterons have the increased bus bandwidth
>> (which helps greatly in the transcoding) and redundancy on their side.
>>     
> I think just about any reasonably modern machine will do fine for you. A 
> backend really doesn't have much of a CPU requirement in normal DVR 
> operation, disk I/O being more important. CPU is required for commercial 
> flagging, transcoding and DVD creation

and playback

> , but all those procesess

except playback

>  can be niced 
> as required, real time not being a factor.

Brian's exactly right.  Backends don't need much.  I have two backends
(one Athlon XP 2400+ master and one Athlon XP 2000+ slave) and one
frontend (Athlon X2 4800+).  I have 4 pcHDTV HD-3000's (high-def capture
cards) and the backends have no problems keeping up (happily doing
non-real-time flagging and transcoding).  The /only/ reason that I have
2 backends is power draw--I couldn't find a power supply (and even tried
some >600W PSU's) that could handle 4 HD-3000's (I actually found that
cheap PSU's gave me better results than expensive/new/gaming-style PSU's).

If you go use standard definition (don't know whether your DVB-T is
high-def or not), you definitely won't have a problem.  I also maintain
a system for a friend that has an Athlon XP 2000+ and 512MB RAM and 4
PVR-250's (the card that was replaced by the PVR-150) and acts as a
combined frontend/backend and a lot of other things (web server, FTP
server, ...).  It's never had a problem--even recording 4 shows while
playing back a 5th while the web server and FTP server are in use.  I've
never used RAID on it, either.

And, IMHO, RAID is unnecessary and probably not much benefit once you
upgrade to 0.21 (once it's released).  The only benefit RAID will
provide is redundancy--it may actually lower read/write performance. 
With storage groups, by simply having as many (or, better, more)
filesystems than capture cards, you can actually parallelize writes so
only one recording is written to each filesystem at a time.  If each
filesysem exists on a separate disk, 2 disks = 2x the read/write
performance.  See
http://www.gossamer-threads.com/lists/mythtv/users/278745#278745 and
http://www.gossamer-threads.com/lists/mythtv/users/278818#278818 and
http://www.gossamer-threads.com/lists/mythtv/users/278823#278823 . 
(Though RAID may still be nice for your non-Myth file server storage.)

IMHO, the only benefit of dual CPU over dual core is that you can put 2
dual-core CPU's (or 2 quad-core CPU's) on the board.

BTW, the above is all my opinion (so please don't hold me responsible if
you find it's not what you want after purchasing).

Mike