HI Rob, > We'd only be recording some programmes. We've enough experience of > enterprise systems to build a resilient backend (though we'd have > to look at how we'd do failover on the master backend - the SPoF > of the system). How many quad opterons (Sun do the nice v40z) > would it take to transcode say four programmes simultaneously? > Could one server handle 4 DVB capture cards? What's the first > bottleneck people hit - the PCI bus? hard drive speed?
My current system has 4 DVB-S cards, no problems at all with 4 simultaneous recordings. Single P4 2.4Ghz. If you want to keep these recordings as references copies I'd advice you not to transcode; after all you do lose quality in the process, and the mpeg2 streams you get off a DVB card are already in a reasonable format for archiving. I'm currently using 3 different models of cards in my system: 2x Terratec Cinergy 1200 DVB-S: basic card without support for CI modules. 1x Hauppauge Nova-CI-S: used with cryptoworks CI module and ORF smart card for austrian programs. 1x Hauppauge Nexus-S: used with premiere CI Module and smartcard. Without requirement for CI modules I'd probably stick with the terratec cards; small, don't run too hot and no problems so far. Also, the dvb mpeg2 recordings can contain multiple audio streams (multiple languages, different formats) - these will be recorded just fine in mpeg2 format. Transcoding usually removes all but one of these audio streams. So, where can you expect bottelnecks to appear in your system? - Cooling/Power Supply: Capture Cards (including DVB) create quite a significant thermal load; shouldn't be an issue with real server class hardware, but can fry badly cooled systems, especially small-form-factor stuff. - PCI Bandwidth: the DVB Recordings I get are somewhere in the 5-8Mbit/s range. That'll give you 32Mbit Input for 4 cards; take x2 because you'll probably want to store it somewhere as well. Still comfortably below the bandwidth of a single PCI bus. - Storage Subsystem: at ~ 1Mbyte/s per recording certyinly no problem for local storage and 4 Cards; 30 channels on a shared storage server should also be possible with a bit of planning. Bye, Martin
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