[mythtv-users] Gig Network

ryan patterson ryan.goat at gmail.com
Sat Mar 10 13:47:26 UTC 2007

On 3/10/07, Blammo <blammo.doh at gmail.com> wrote:
> On 3/9/07, Henrik Beckman <henrik.list at gmail.com> wrote:
> > Multiple streams probably is harder on the drives than on the network,
> does
> > anyone have som experience on how many streams SDTV and/or HDTV is
> >doable to a single spindel, without to much fragmentation (how large
> "blocks" are
> > written by myth?)
> There seem to be people who have "miracle drives" who claim record 4
> streams of HD, commercial flag, transcode, and watch 2 HD streams at
> the same time, all off one single spindle, one single drive, one
> single computer, integrated FBE/SBE.
> I am not one of those people. It would have been so much cheaper if I
> was.....
> I discovered early on in my testing that a single spindle, even with
> sep front/back ends, was only good for about 1 stream of intensive
> usage at a time. What I mean by that is all operations, on a single
> stream. IE, record 1, playback 1, commercial flag 1, on a single
> drive.
> Increasing any of those things to 2 or more, IE 2 tuners, 2 commerical
> flaggers, and you start seeing small problems with a single drive. You
> end up with "write timeouts" or "chunk/chop" in recordings, or sloppy
> playback, or etc.. not all the time, not every program, but it starts
> creeping in. You might be able to record 3 tuners, but as soon as
> commercial flagging starts in, you start seeing complains of "write
> timeouts" and your recordings start going to hell.
> The other thing that will tap the single drive (and tap 100Mbit
> ethernet) is Fast Forward and Rewind. You can flatline 100Mbit
> ethernet easily with anything over about 10x. With GigE you can run it
> well over 200Mbit, which is 20MB (roughly) which is about half of the
> sustained read rates (without concurrent seeks) of most current
> drives.. (which average 40MB to 50MB of real throughput a second)
> Commercial flagging, especially during the "logo detection" phase can
> slam the drive(s) with the same amount of demand.
> My current setup, of 4 tuners, 3 frontends, all HD, realtime
> commercial flagging, 2-3 transcoding sessions a day...... is
> impossible on a single spindle with any high percentage of success.
> But again, that's just me... maybe someday I'll find the "magic"
> drive. Till then it's just me and my raid array.. (oh how I love
> 3ware)
My setup isn't quite as demanding as yours (4 HD tuners, 1 SD tuner, 1
networked frontend) but I have not seen any bottleneck issues with drive
performance.  Even when recording several HD shows and watching another.
Have you tried increasing the PCI latency setting in your motherboard setup

Ryan Patterson
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