[mythtv-users] network card

[Raymond Wagner]

> On May 6, 2014, at 13:29, Jim Stichnoth <stichnot at gmail.com> wrote:
> 
>> On Mon, May 5, 2014 at 7:46 AM, Gary Buhrmaster <gary.buhrmaster at gmail.com> wrote:
>> On Mon, May 5, 2014 at 11:16 AM, Wayne Roberts
>> <wayne at therobertsfamily.eu> wrote:
>> > Hi all,
>> >
>> > I am in the process of shopping for my backend, and was wondering what
>> > network card you "should" use (speed) ?? Is gigabit going to be fast enough
>> > or should i push the envelope and go 10 gig?
>> 
>> *Usually*, 1Gb/s networks are sufficient.
>> 
>> You did not state what your services you backend is going to be supporting
>> (especially if it will be a "shared" system).  For a BE, how many networked
>> tuners, how many active frontends?  A HD stream usually fits in (less than)
>> about 20Mb/s, so you could be recording from 10 simultaneous network tuners,
>> and playing back concurrently to 10 frontends and still be at no more than 40%
>> network utilization with a gigabit card on a dedicated BE (and likely much less,
>> since most HD content is not 20Mb/s).  At those rates, your disk subsystem
>> would probably need more attention than your network.
>> 
>> As with all else, your mileage will vary.
> Years ago, I wanted to justify upgrading from 100-megabit hardware (i.e. switches) to gigabit.  I set up 4 simultaneous recordings, on 2 dual-tuner OTA HDHRs, all on different multiplexes, with the highest-bandwidth broadcasters I could find.  I was not able to saturate the network and get corrupted recordings.  I had to use other justifications (like, "it just feels right") to upgrade.
> 
> I didn't try playing recordings on all three frontends at the same time as the 4 recordings, but I think it's safe to say that 1Gb/sec will do for almost everyone.

Four HD channels will run you 50-60Mbps.  With TCP, that's not a problem.  With UDP and an application layer that retransmits, that's not a problem.  With no retransmission and more than two devices on the network, that's about the limit.  You're nowhere near saturated, but your risks of collisions beyond the ability of the switch's packet buffer to handle increases significantly.  Unhandled collisions mean data loss.  If using multirec with cable, you can easily double that rate.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.mythtv.org/pipermail/mythtv-users/attachments/20140506/18a6d43e/attachment.html>