[Bug 10322] Slow Performance over Network rsync

[samba-bugs at samba.org]

https://bugzilla.samba.org/show_bug.cgi?id=10322

--- Comment #11 from Linda Walsh <samba at tlinx.org> 2013-12-24 21:47:56 UTC ---
samba-bugs at samba.org wrote:
> https://bugzilla.samba.org/show_bug.cgi?id=10322
>
> --- Comment #5 from roland <devzero at web.de> 2013-12-24 01:28:45 UTC ---
> i installed 64 bit cygwin on my windows8 system and compared the cygwin builtin
> rsync 3.0.9 to self compiled rsync 3.1.0 and 3.0.8. surprisingly, both 3.0.9
> and 3.1.0 are fast (~30mb/s) BUT(!) 3.0.8 is about half as fast (~15mb/s). i`m
> using a fast ssd, though so i`m not sure how well it performs with ordinary
> hdd. i never heard of any throttling mechanism in windows or cygwin, but all
> our observations are weird indeed and need explanation. i also have no clue
> what`s going on here.
>   
===============
What's going on is you are using something designed for remote comparisons over
a slow link:

/h> time rsync --progress --stats 128M 128Ma
128M
  134217728 100%    7.15MB/s    0:00:17 (xfer#1, to-check=0/1)

Number of files: 1
Number of files transferred: 1
Total file size: 134217728 bytes
Total transferred file size: 134217728 bytes
Literal data: 134217728 bytes
Matched data: 0 bytes
File list size: 19
File list generation time: 0.005 seconds
File list transfer time: 0.000 seconds
Total bytes sent: 134234177
Total bytes received: 31

sent 134234177 bytes  received 31 bytes  7255903.14 bytes/sec
total size is 134217728  speedup is 1.00
18.31sec 0.17usr 0.14sys (1.69% cpu)

time bash -c "cp 128M 128Ma; sync"
1.98sec 0.21usr 0.66sys (44.58% cpu)
time dd if=128M of=128Ma bs=128M oflag=direct
1+0 records in
1+0 records out
134217728 bytes (134 MB) copied, 0.801389 s, 167 MB/s
1.00sec 0.03usr 0.20sys (23.30% cpu)

----


      Notice rsync takes 9 times as long as cp and 18 times as long
      as dd.

If I specify a 4k blocksize with "dd":
time dd if=128M of=128Ma bs=4k oflag=direct
32768+0 records in
32768+0 records out
134217728 bytes (134 MB) copied, 10.5946 s, 12.7 MB/s
10.81sec 0.17usr 1.91sys (19.31% cpu)
-----------
A 2k blocksize:
time dd if=128M of=128Ma bs=2k oflag=direct
65536+0 records in
65536+0 records out
134217728 bytes (134 MB) copied, 19.1194 s, 7.0 MB/s
19.31sec 0.28usr 3.78sys (21.06% cpu)

==============
All of the above were conducted on Win7x64 using cygwin32.

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