[CentOS] minimize download bandwidth techniques

[John Summerfield]

Wojtek.Pilorz wrote:
> On Thu, 12 Apr 2007, John R Pierce wrote:
>> Dale Sykora wrote:
>>> I know of a few techniques for minimizing server bandwidth when
>>> bittorent is not an option.
>>>
>>> 1) If you have the beta isos, you can rename them as centos 5 isos and
>>> then rsync from a mirror that allows rsync (such as kernel.org).  Then
>>> only changes from beta to centos 5 plus some overhead is downloaded.  I
>>> suppose you could use this technique with bittorrent too.
>>>   
>> if one file near the beginning of the ISO changes size by even a block, 
>> then the whole rest of the ISO will be different, this will gain you 
>> nothing.
> With bittorrent, that is perhaps true.
> Rsync will be able to handle that difference. But if most RPMs are rebuild 
> that it will have not much matching data.

By way of example, I had a recent daily build of Debian Etch (mid 
March). When Debian released (must be a blue moon!) earlier this week, I 
rsynced the three DVD images. rsync did it really quickly, and claimed 
over 1 mbyte/sec on an ADSL 256k incoming link.

Another example; a few years ago I had a broken ISO that rsync would not 
fix, it was the same size and timestamp as the original, and 
checksumming was forbidden.

I pruned a little off by copying about 1k less with dd, then rsync did 
fix it. (wonders why touch didn't work. hmm.)




-- 

Cheers
John

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