[mythtv-users] Gig Network

Blammo blammo.doh at gmail.com
Sat Mar 10 05:29:51 UTC 2007

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

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

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