[mythtv-users] Killer system or overkill?
crunchyfrog at charter.net
Tue Dec 13 16:39:58 EST 2005
Raphael Pooser wrote:
> As people here have said, your system is pretty much right on for an
> HDTV set up that could say, transcode at the same time as watching live
> TV for instance. For just watching straight live TV or HDTV recordings,
> as someone else said any fairly recent athlon64 variant (like a 3200+ as
> you were thinking) would do. As to the question about more RAM, true
> that in linux the ram you give it the more it can use and the more stuff
> you can have open, unlike in windows with most of its applications.
> However, if I was going to choose between one more gig of ram or going
> from one to dual core, dual core would definitely win out. Mainly the
> only performance increase you are gonna get is in the RAID (from the
> benchmarks quoted in above post), but since you don't need anything
> anywhere nearly close to that level of performance as you already knew,
> the extra 1GB or RAM is pretty much wasting money. I don't know how I
> could possibly get mythtv to actually fill up a gig of RAM at any rate.
> Maybe a backend connected to 5 or so frontends?
Thanks. Your response (and others) matches what I'd expected to hear:
dual core if I want to do something else CPU-intensive (like transcode)
as well as run myth. I still don't see -- as you obviously don't -- how
an extra GB of RAM will improve things much. I'd have to be doing
something else on the system that did heavy I/O or otherwise could use a
lot of RAM. Capture of data from an HD card gets data at a very flat
rate: either you keep up or you don't. Basic queueing theory shows
that if the arrival rate is near constant you won't get a big queue (for
disk output). Consequently, beyond the minimum amount of buffering
needed to keep up and a bit of headroom for safety, a huge buffer cache
will just hold things that aren't going to be read back any time soon
any way. The benchmark referred to was for a different kind of load on
the RAID system.
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