Why does't rsync use delta-transfer for local files ?

Posted by o_O Tync on Super User See other posts from Super User or by o_O Tync
Published on 2011-01-17T13:59:14Z Indexed on 2011/01/17 17:55 UTC
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linux

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rsync

I have a big iso image which is currently being downloaded by a torrent client with space-reservation turned on: that means, file size is not changing while some chunks in in (4 Mib) are constantly changing because of a download.

At 90% download I do the initial rsync to save time later:

$ rsync -Ph DVD.iso /some/target/
sending incremental file list

DVD.iso
       2.60G 100%   40.23MB/s    0:01:01 (xfer#1, to-check=0/1)

sent 2.60G  bytes  received 73 bytes  34.59M bytes/sec
total size is 2.60G   speedup is 1.00

Then, when the file's fully downloaded, I rsync again:

total size is 2.60G   speedup is 1.00

Speedup=1 says delta-transfer was not used, although 90% of the file has not changed. Why?!

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