[mythtv-users] Faster CPU and more RAM in SD frontend or backend?

George Mari george_mythusers at mari1938.org
Tue Jun 3 01:28:29 UTC 2008

Johnny Russ wrote:
> I currently have a combined frontend/backend for SD only. It is a PIII 1
> GHz, 384 MB of RAM, PVR-150 tuner, and 2 x 160 GB PATA drives. It barely
> manages to get by. I can't record and watch TV at the same time unless I use
> XvMC. A friend just gave me an old system he didn't need. So I am thinking
> about finally having a separate frontend and backend. The donated system has
> a 2.4 GHz Celeron, 768 MB of RAM, 40 GB PATA drive and 2 x 250 GB SATA
> drives. I would like to hear some opinions on the best way to split the
> hardware up between the sytems.
> Currently I am planning on putting the 2 160 GB drives and the 2 250 GB
> drives into a software RAID array, with the PIII and 384 MB of RAM, on the
> backend and tucking it away with the router in the basement. 

I agree with making the P3 the backend, although 384MB is on the low 
end, it should be OK.  It depends on how many tuners you have and 
whether you will have anything else running on the box.

Stuffing 4 drives in the case, make sure there is  good airflow over 
those drives.

With 2x160GB and 2x250GB drives, will you make a 4x160 RAID5 or RAID0?

> Then use the 40
> GB drive with the Celeron and the 768 MB of RAM in the frontend. The
> frontend will connect wirelessly from the living room. 

I don't have direct experience myself, but people on the list report 
some trouble with wireless, but you should be fine with SD and 
especially 802.11g.

> I feel most uncertain
> about where the CPU/RAM will affect my overall performance the most. 

I think you'll be happier with more CPU on the frontend.  You can use 
just plain Xv with your Nvidia card on your 2.4ghz celeron no problem. 
Easier to setup, more of a performance margin.

BTW - I had until recently a frontend-only 450Mhz P3 with a Nvidia 5200 
and XVmc doing SD just fine.  Sure it was maxed out, but it played video 
with no hesitation at all.

> I am
> not sure what kind of CPU/RAM requirements the software RAID has. 

My dedicated backend has 2 x P3 600Mhz with 589MB of RAM, and a SCSI 6 x 
181GB software RAID 5.  Recording two streams simultaneously, the RAID5 
process never goes above 5%.

> I would
> occasionally be simultaneously streaming to the Mythfrontend and to XBMC on
> an old Xbox. I also occasion transcode some stuff to Xvid for long term
> storage. Does that need to be done in the backend? 

Transcoding is usually done as a user job, setup in the backend.  I 
think people may have setup a tuner-less slave backend on their 
frontends to do this sort of thing, but I have no experience myself.

> My frontend will be
> hooked up to a standard SD television via svideo out of an Nvidia 5200 card.
> Is this a decent arrangement or is some other arrangement of the hardware
> better?

Looks good to me - you should get appliance-like performance.  Good luck.

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