Paul Slootman wrote:
On Wed 22 Mar 2006, Linus Hicks wrote:
Paul Slootman wrote:
I'd recommend doing --inplace, as chances are that data won't move
within a file with oracle data files (so it's not useful to try to find
moved data), and copying the 4TB to temp. files every time could become
a big timewaster. Also the -t option could be handy, not all files
change all the time IIRC.
The above remark about not being "useful to try to find moved data"
provoked an idea. But my understanding of --inplace is apparently different
from yours. I thought --inplace only meant that the destination file would
be directly overwritten, not that it would turn off any of the
optimizations for finding moved data.
I go on what's in the manpage:
--inplace
This causes rsync not to create a new copy of the file and then move it
into place. Instead rsync will overwrite the existing file, meaning
that the rsync algorithm can't accomplish the full amount of network
reduction it might be able to otherwise (since it does not yet try to
sort data matches). One exception to this is if you combine the option
with --backup, since rsync is smart enough to use the backup file as the
basis file for the transfer.
Well, it would be nice if it were more explicit about what difference there is
in the "rsync algorithm", because from my experience, I would guess that it does
try to find moved data. What I have seen during my testing on a 1gbit network is
that a large file (I don't remember the exact details, but it was between 1gb -
4gb) took some seven minutes to rsync with no destination file. When there is a
destination file with just a few blocks changed, it took a little longer, and
with a lot of blocks changed, it took a lot longer, like four hours.
Linus
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