rsync - Dec 2008 - rsync and MD5

Hi all!

I've got a question about rsync using the MD5 algorithm.

I know that rsync makes blocks of a file and then compares the checksums of each
block.
If the checksum is unequal the block is tranfered. 
Otherwise it could be that the checksum is the same but the block is different.
Therefor rsync uses a 128 BIT MD5 algorithm.

Now, at what filesize is it better to check the whole file with MD5 and when its
faster just to copy the file?
Is there a formula, table or diagram which it shows? (I think it depends on the
Hardware!)
Unfortunately I didn't find anything.

Thanks a lot.

Spanockel
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That decision obviously depends on processing power and network capacity
available. A recent thread on Slashdot
(http://tech.slashdot.org/tech/08/12/14/162235.shtml) mentioned this
research which might give more insight:
http://www.cs.cmu.edu/~dga/papers/dsync-usenix2008-abstract.html

And btw, I though rsync used MD4, not MD5.

Jeroen van der Vegt	 
System designer 
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> -----Original Message-----
> From: rsync-bounces+jeroen.van.der.vegt=technolution.nl@lists.samba.org
> [mailto:rsync-bounces+jeroen.van.der.vegt=technolution.nl@lists.samba.org]
> On Behalf Of David de Lama
> Sent: dinsdag 16 december 2008 14:34
> To: rsync@lists.samba.org
> Subject: rsync and MD5
> 
> Hi all!
> 
> I've got a question about rsync using the MD5 algorithm.
> 
> I know that rsync makes blocks of a file and then compares the checksums
> of each block.
> If the checksum is unequal the block is tranfered.
> Otherwise it could be that the checksum is the same but the block is
> different.
> Therefor rsync uses a 128 BIT MD5 algorithm.
> 
> Now, at what filesize is it better to check the whole file with MD5 and
> when its faster just to copy the file?
> Is there a formula, table or diagram which it shows? (I think it depends
> on the Hardware!)
> Unfortunately I didn't find anything.
> 
> Thanks a lot.
> 
> Spanockel
> _______________________________________________________________________
> T?glich 1.000.000 Euro gewinnen! Jetzt kostenlos WEB.DE MillionenKlick
> spielen! https://millionenklick.web.de/?mc=mail@footer.mklick@home
> 
> --
> Please use reply-all for most replies to avoid omitting the mailing list.
> To unsubscribe or change options:
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> Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html

That decision obviously depends on processing power and network capacity
available. A recent thread on Slashdot
(http://tech.slashdot.org/tech/08/12/14/162235.shtml) mentioned this
research which might give more insight:
http://www.cs.cmu.edu/~dga/papers/dsync-usenix2008-abstract.html

And btw, I though rsync used MD4, not MD5.

Jeroen van der Vegt	 
System designer 
________________________________


Ok, i will check the two links, thanks!

"Version 30 of the protocol (released with rsync version 3.0.0) now uses
MD5 hashes rather than MD4."
http://rsync.samba.org/ftp/rsync/src/rsync-3.0.0-NEWS


David
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