[streaming] Re: Streaming Large Amounts of Data

[Daniel Balog]

On Fri, 2003-05-23 at 00:08, Geoff Baker wrote:
> Good-day,
> 
>   I am curious, what is he largest amount of data that you have been able to
> get out of a machine running video lan.  I am hoping for a number around
> 900Mbps (effectively filling a gigabit Ethernet).  Thanks
> 
> -Geoff Baker 

I usually just read this list, but i've done some work on high bandwidth
applications of streaming, so i thought i'd butt in ;)

The key here is disk speed.

You could probably do that if it is _not_ random disk reads that are
streamed, eg. if you stream a hundred 9 mbit streams of the same data,
it would probably be possible. 

If it _is_ random access you need, (vod etc.) you'll have problems
saturating a gigabit link, disk speed will be the bottle neck.

Even if i haven't tried this with vls but only other streaming-servers,
you'd probably want to use a quite large array of disks with the files
in multiple places for speed etc. (multiple controllers even)

And on top of that i'd probably write some round-robin stuff for reading
from different arrays etc.

If i just let myself do a quick top-of-my-head calculation here;

900 / 8 (bits per byte) = 112.5 (this is the minimum megabyte per second
_sustained_ read you'd need from disk to somewhat reliably get 900 mbit)

And if you then take overhead in all the layers in accound you'll see
that's quite an extreme disk ;D

_Though_, on the plus side; most of the disk access in a real world
situation is cached, so you can probably count on the minimal
configuration and get the desired result with that.

If it's multiple streams from the same source it'd probably be ok.

Another thing i almost forgot: if you need to dedicate bandwidth
throughout the whole system, from disk to nic, take a look at irix, it
has cool tools for managing this and making a system "guarantee" a
bandwith from disk to daemon etc.

-- 
Balog


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