Re: fragmentation

Pe data de Mar 02 Noi 2004 13:49, a-ţi scris:
> My observation is that when starting additional downloads, Valknut
> finds the biggest incomplete block and starts in the middle of it. 
> This gives the download as large chunk to get before it needs to
> reconnect for another block.  However its probably not optimal when
> there is another download working on that block, as it 'cuts in
> front' of the existing download and fragments what was a contiguous
> piece.

whether is optimal or not depends on the speed of the other download; 
if are of equal speeds middle is the answer, if it's a lower speed 
tail is best, and so on.

i don't know how to pre-determine the speed of the future download 
(the speed setting in client may not be accurate), so it will always 
be a guess. i thing the middle is ok.

what is bad is that, even when exists another "idle" fragment, (little 
or big), this isn't choosed as a starting point.
>
> Beginning a new download at the start of an existing fragment is
> probably a good idea, as this would tend to 'clean up' smaller
> fragments first and tackle big chunks later.  
No tackle big chunks later, what i say is that if there is a chunk 
which is not being downloaded, it could start at its beginning, 
regardless of its size (it could be the biggest cunk left as well).

> This would be the 
> opposite of the current method, where the big chunks get started
> first, leaving many small fragments for the 'end game' which is the
> problematic last few percent of the file.  
No, it wouldn't be opposite, because when all chunks are being 
downloaded it will choose the middle of the biggest one.

> How this would actually 
> effect overall download efficiency is hard to judge.

i think it will diminish the chance of getting "no free slots" in the 
end of the downloading and also you'll have less time wasted with 
reconnections.

>
> Regards,
> Andrew Greig
> aka Mayhem

ghrt