[mythtv-users] Enough power?

[Brad Templeton]

On Tue, Jan 18, 2005 at 09:54:12PM +0100, Jens Peter Vilstrup wrote:
> This might be slightly OT. Sorry if I offend anyone.
> I'm in the planning phase of my MythTV project, but unsure if my
> planned myth-backend has enough oomph.
> I have:
> Tyan Tiger MP with dual 1.4Ghz Athlon XP's and 1GB of RAM.
> Gbit NIC.
> 2x PVR-250 cards.
> Some yet-to-be-determined SATA(n) card(s), possibly RAID (that, or
> software RAID).
> A whole lot of harddrives.
> MySQL will be on a different server.
> 
> I want to be able to record two shows simultaneously, while watching
> on two frontends, while copying files at 100Mbit to or from a client
> PC...
> In your experience, is this a feasible goal?

More than feasible, your backend seems to be overpowered.  PVR-250
effectively capture video with effectively no CPU cost, just a few
percent on an Athlon 750mhz, for example.   I see no reason why
a single machine of just about any stripe could not do what you
describe (except the software RAID, that might require some CPU)

There is a network limitation.  If your frontends are on the same
network as the PCs that are saturating the 100mibt network, then
a saturated net is a saturated net.  I don't know about gbit networking
but with 100mbit the rule was that a 10mbit client on the network takes
10x the bandwidth it is using, because it is time that matters.   Ie.
if gbit works the same, then a 100mbit client connected to the switch
uses all of the switch if it is using the full 100mbit, it doesn't
use 10% of the switch.  

Recording from pvr-x50 cards and pchdtv cards takes almost no CPU power
at all.   Things that take CPU power are playback (on that machine)
and complex SQL queries.  (For example, I have found that by putting
100 record-wishlist searches into Myth, the database takes a minute
to recompute the recording table every time I make a change, but this
is rather extreme.)