[mythtv] Thoughts on encoder farms / distributed capturing and viewing

[Isaac Richards]

On Friday 01 November 2002 04:52 pm, Robert Middleswarth wrote:
> I just tried this at home I xfer 3 7??M files from a Redhat 7.3 Box to a
> Redhat 8.0 Box and my Xfer rates were 5mb accroding to the FTP Client.
> NFS might be faster then FTP but still the max I am getting is 5mb over
> my cheapo switch and intel / reltek 8139 cards.
>
> If you use the rtjpeg codex which produces files optmized for Speed not
> size you aren't going to be able to do more then 2 streams.  If I am
> rembering correctly I have seen number for 2.5 to 3.33 megs for MPEG4 so
> if you say only 3 Megs for rtjpeg and say get around 6 Megs can be
> xfered then 2 Stream would work fine but more then that would require
> some form of load balancing multi-nic card.  If I screwed up the number
> some place let me known as conversion between Bytes and Bits get
> confusing and could make my number off by a factor of 8.
>
> After running that test I was think there might be some limits based on
> HD Speed and I think both machines have DMA off so that could be
> improved.  However I doubt it will go from 5 to 30.

It takes roughly 2 minutes 20 seconds to transfer a 1.4 gigabyte file (a one 
hour show) using ftp from my mythtv box to my webserver.  The webserver's got 
a _slow_ disk, too, maxes out at 14MB/s according to hdparm.  Anyway, that's 
10.6 megabytes/sec, only something like 25.8 times more than the ~420 
*kilobytes*/sec that the stream would require to transfer/playback the file 
live.  I don't think there'll be any problems transfering a few files live to 
different settop boxes, if that's what you wanted to do.

If you don't have DMA turned on, you're limited in transferring large amounts 
of data to disk speed.  Which, without DMA turned on, is usually painfully 
slow, as you've just seen.

Isaac