Hi,
I'm not an rsync expert, other people will confirm or infirm what I'm
saying, but I think your problem is that you are using rsync in "stand-
alone" mode to copy from and to the same computer. Although that
works, in this way rsync won't use it's delta algorithm and so, won't
have great performance.
That may be wrong, but what I understood from my readings is that
rsync has been made for network transfers from computer A to computer
B that always share some of the data. In this configuration and with
rsync running in both ends, it will use the delta algorithm to do not
transfer all the files, but only the needed pieces of files needed to
reconstruct the whole files in the other end. This optimisation aim to
save bandwidth first, and have the side effect to be faster than an
entire copy because of hard links and other stuff that avoid the
computer B to write all of the data.
As I said, I not sure of what I'm saying. I think this is right and
that's the reason you don't see any optimisation in your
configuration, but I would prefer someone else to confirm my hypothesis.
Best regards,
Vitorio
Le 21 sept. 10 à 09:00, grarpamp a écrit :
I have a 5.5GB file, mostly sparse. Tar performs far[!] better than
rsync.
I have no ideas yet, so just an FYI as to current state.
FreeBSD 8.1 i386 zfs
Yes, I know the blocks used differs but don't know why yet, could
be just how zfs does things or related to the large amount of
sparseness.
There are no media errors, CPU/IO load or anything like that and the
source
and dest paths are on the same filesystem.
I've not tested times for files that are, say, 90% full instead of
90% sparse
Though a 50% 35MB file was 8.5x slower than tar and had identical
block counts and sha256 with both.
/usr/bin/time rsync -HaxiS ./a ../
f+++++++++ a
271.13 real 101.44 user 95.62 sys
l -s ./a ../a ; rm -f ../a
blocks bytes
3625 5535932416 ./a
3769 5535932416 ../a
/usr/bin/time tar -cf - ./a | /usr/bin/time tar -C .. -Sxf -
57.67 real 1.10 user 27.77 sys
57.67 real 10.68 user 5.87 sys
l -s ./a ../a ; rm -f ../a
blocks bytes
3625 5535932416 ./a
2977 5535932416 ../a
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