Need hint for my question regarding the working of rsync.
patrickpollen2 at gmail.com
Tue Nov 12 23:24:35 MST 2013
>> These are both a weak and a strong checksum for each chunk of the file
from start to finish.
So lets take an example.
If a file were 70000 bytes and the logical block size for rsync by default
being 700, it would send :
1) 4 Bytes x 70000/700 = 400 Bytes
2) 16 Bytes x 70000/700 = 1600 Bytes
Total : 2000 Bytes
Is this correct ?
On Wed, Nov 13, 2013 at 3:55 AM, Kevin Korb <kmk at sanitarium.net> wrote:
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> First, are you talking about --checksum checksums or the hashing of
> files that are different on both ends so that only the differences
> need to be transferred? You seem to be talking about the latter while
> describing the performance of the former.
> If you are talking about --checksum then you should know that it is
> only there for a few very unusual use cases. It most normal(ish) use
> cases --checksum is slower than simply re-copying everything and
> especially re-hashing everything (--ignore-times).
> On 11/12/13 17:13, Karl O. Pinc wrote:
> > On 11/12/2013 03:50:20 PM, Wayne Davison wrote
> >> Yes, the receiver sends all the checksums that it generates at
> >> once
> >> For really big files it would be interesting to amend this rule
> >> to one where the sending side waits only long enough for a
> >> certain number of checksums to arrive before it begins its work
> >> (and perhaps pauses if it gets too far ahead of the arriving
> >> checksums).
> > Based on the behavior I see when using rsync, without really
> > knowing what's going on, it seems that the sending side first does
> > a lot of disk access, then the receiving side does, and then the
> > sync begins over the network. It would save a lot of wall-clock
> > time if the sending and receiving side could both be hitting the
> > disk at once. At least in my use case, with whatever version of
> > rsync I happen to be using.
> > Karl <kop at meme.com> Free Software: "You don't pay back, you pay
> > forward." -- Robert A. Heinlein
> - --
> Kevin Korb Phone: (407) 252-6853
> Systems Administrator Internet:
> FutureQuest, Inc. Kevin at FutureQuest.net (work)
> Orlando, Florida kmk at sanitarium.net (personal)
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