Re: [rdiff-backup-users] Re: more info on 25gig files

>>>>> Donovan Baarda <[email protected]>
>>>>> wrote the following on Fri, 06 May 2005 15:47:10 +1000

> I forget the exact formula for the blocksum size (something to do
> with the ln2 of the number of blocks), but the blocksize was
> definitely the sqrt of the filesize. There are lots of reasons why
> this is a good heuristic... it compensates for the way lots of
> things scale in the rsync algorithm against file size (execution
> time, probability of blocksum collision, etc)

Ok, so by sqrt you mean sqrt rounded to the nearest 512, with a
minimum of 512?  Is 512 a magic number in some way?

> So yeah, I'd definitely switch to the sqrt thing, you will get a lot
> less grief as files get larger.

By grief you mean in terms of running time and/or memory usage?  Or
are using too-large block sizes actually incorrect, and not just
inefficient?

> I keep meaning to look at that stuff and update stuff in pysync and
> librsync. The other one worth looking at that has recently appeared is
> zsync. Something to do _after_ moving from Melbourne to Dublin :-)

A big change :)  I hear both are nice places (not been to Melbourne
yet though).


-- 
Ben Escoto

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