[bittorrent] BT for serving smallish (3MB) files

Gary Robinson grobinson at goombah.com
Sat Feb 4 16:37:17 EST 2006


> I have personally found that, even with smaller files such as the 3mb
> files you're looking at using, that BitTorrent is a viable way to reduce
> load on the central servers for the files. Actual performance may vary
> depending on the popularity of the files.

Thanks -- can you give me any more details such as a reasonable 
expectation of percentage of server bandwidth saved (assuming many 
downloaders)? In another response to my original query, Olaf said that 
each tracker request costs about 1K. I'm not clear on how many tracker 
requests there are per file download. I'm just starting to study the BT 
protocol -- maybe I can figure it out that way, but I trust actual 
hands-on experience more.

> Trackerless torrents aren't without their problems. If you're going to
> use them extensively, make sure the .torrent file contains IP and Port
> information of a system in your configuration that will basically always
> be on (to be used as a common DHT entry point). Make sure this node has
> its listen port open to UDP traffic as well as TCP traffic. The load
> that would normally go to the tracker (which isn't really that much)
> would go to the DHT nodes instead.

What if, in order to REALLY minimize server load, we DON'T do that? 
Wikipedia (http://en.wikipedia.org/wiki/Distributed_hash_table) says 
that a distributed hash table has guaranteed routing. If that's true 
then theoretically, as long as there are clients making the files 
available, everything should be fine.  But of course theory isn't 
always reality. Can you give me more detail on why you give the advice 
above?

This feedback is very helpful, thanks!

Gary


-- 

Gary Robinson
CTO
Emergent Music, LLC
grobinson at goombah.com
207-942-3463
Company: http://www.goombah.com
Blog:    http://www.garyrobinson.net

On Sat, 04 Feb 2006 17:24:52 -0400, Harold Feit wrote:
> I have personally found that, even with smaller files such as the 3mb
> files you're looking at using, that BitTorrent is a viable way to reduce
> load on the central servers for the files. Actual performance may vary
> depending on the popularity of the files.
> 
> Trackerless torrents aren't without their problems. If you're going to
> use them extensively, make sure the .torrent file contains IP and Port
> information of a system in your configuration that will basically always
> be on (to be used as a common DHT entry point). Make sure this node has
> its listen port open to UDP traffic as well as TCP traffic. The load
> that would normally go to the tracker (which isn't really that much)
> would go to the DHT nodes instead.
> 
> Gary Robinson wrote:
>>  Hello,
>> 
>>  My company has an application (http://www.goombah.coom) that uses 
>>  BitTorrent internally to distribute some largish (50MB) data files it 
>>  needs to pass around. (The  app is written in Python, if you're 
>>  interested.)
>> 
>>  This is a music recommendation app, and it allows users to acquire 
>>  (legal) music files. This are typically much smaller than the files 
>>  mentioned above -- they tend to be in the 3MB size range. I have heard 
>>  it said that BT isn't worth it for files less than 10MB. But, we would 
>>  like to get the load for serving the files off of our servers and 
>>  spread among the clients.
>> 
>>  So, a series of questions:
>> 
>>  1) With 3MB files, and many people downloading each one at once, is 
>>  there  still significant server bandwidth using a BT tracker compared 
>>  to just serving the files? Does anyone have any statistics?
>> 
>>  2) How well does trackerless BT work at present? Under the 
>>  circumstances laid out in (1) above, what would the pros and cons be? 
>>  It seems that, at least from the perspective of our server load, it 
>>  would eliminate the question of whether it would be worth it to use BT 
>>  for files < 10MB, since there is no tracker load.
>> 
>>  Many thanks for any help anyone can give with these questions.
>> 
>>  Gary
>> 
>>    
> 
> 



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