[mythtv-users] RAID versus Drobo
James Gutshall Jr
warchildx at gmail.com
Mon Sep 10 20:14:41 UTC 2007
Though some newer boards offer SAS controllers on board which are also
backward compatible with SATA drives.
On 9/10/07, Brian Wood <beww at beww.org> wrote:
> Eric Robinson wrote:
> > Brian Wood wrote:
> >> Eric Robinson wrote:
> >>>> Have a look at this:
> >>>> Of course if you plan to record one stream while watching another,
> >>>> record multiple streams, or do anything else requiring disk I/O at
> >>>> 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
> >>> 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:
> >> (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,
> > though:
> > "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)...?
> They can send multiple videos. That speed is the "transport stream",
> which can contain one or more "program streams".
> > Either way, I think I'm fine with software SATA RAID-5...
> Agreed, totally.
> With PC hardware you're not going to get anything faster than ATA in
> either the P or S incarnation. You'd have to go to SCSI drives, and even
> then most consumer mobos have only 32-bit PCI slots and most U320 cards
> want a 64-bit controller, as do most hardware RAID5 cards.
> I have heard of PCI-Express RAID cards, but I don't know anything about
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