[mythtv-users] RAID versus Drobo

Eric Robinson ryunokokoro at gmail.com
Mon Sep 10 19:39:21 UTC 2007

Brian Wood wrote:
> Eric Robinson wrote:
>>> Have a look at this:
>>> http://library.creativecow.net/articles/gerard_rick/premiere-pro-HD.php
>>> Of course if you plan to record one stream while watching another,
>>> record multiple streams, or do anything else requiring disk I/O at the
>>> same time you'll want more than that chart implies.
>> Umm... If you're pointing to the graph on that page then it's a little
>> different.  That's completely Raw HD.  Nothing in MythTV is done in
>> Raw.  My understanding is that it's Mpeg2 generally and can be converted
>> using Mythtranscode to some version of mpeg4.  In any event, I figure
>> MythTV buffers a certain portion of the video on the frontend before
>> beginning to play in case of heavy network jitter.  One hour of 1080p
>> content is 7GB or so, right?  I feel like I read that somewhere in the
>> docs...  Anyone have any success stories with playing back HD content
>> and with what drive interface speed?
> Ooops, right you are. I confused your thread with another from another
> group and sent you the wrong link.
> You might look at:
> http://broadcastengineering.com/news/broadcasting_psip_data_broadcasting/
> (though it's a bit dry and obscure), or:
> http://en.wikipedia.org/wiki/ATSC_Standards
> Basically the full G3 data rate for an ATSC transport stream is 19.4
> Mbps, so if your storage system can handle that you should have no
> problems with a single stream, even if it's using the full available
> bandwidth (which most don't).
> I've had no problems playing back HD (as the original MPEG2 or MPEG4
> (H264-2)) from a single PATA or SATA drive. I haven' tried multiple
> streams but from the specs it should work for 2 or even 3 streams
> without trouble.
Ahh, good stuff!  The Wiki link you sent has this for the actual quote,
"Terrestrial (local) broadcasters use 8-VSB modulation that can transfer
at a maximum rate of 19.39 Mbit/s, sufficient to carry several video and
audio programs and metadata."

I may be misinterpreting an ambiguous sentence but that sounds like
19.39 Mbit/s is for multiple channels?  Or by "programs" do they mean
streams (as in one video with multiple language tracks)...?

Either way, I think I'm fine with software SATA RAID-5...

- Eric

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