Comment 5 for bug 1478800

Efficiency of rsync with compression depends on many variables: content type, processor speed on both sides, network speed, etc.
So I made an investigation for comparison rsync with and without compression.
In this test I used two qcow images with the same size 10Gb:
1. image data consists of text files(copies of nova sources). This image could be compressed very well.
2. image contains copies of ubuntu server iso image. This image couldn't be compressed well.
In test I used processors are Intel i5 2.5Ghz, network speed 1000 Mbps.
In my test I copied each of images with and without rsync compression.
For tests rsync version 3.1.0 protocol version 31 was used.
Results:
1. rsync image with text data without compression:
real 3m37.876s
user 1m6.936s
sys 0m19.919s
user + sys = 87s

2. rsync image with text data with compression:
real 8m16.501s
user 6m55.878s
sys 0m19.695s
user + sys = 436s

3. rsync image with binary data without compression:
real 3m37.846s
user 1m6.098s
sys 0m20.485s
user + sys = 87s

4. rsync image with binary data with compression:
real 8m20.839s
user 6m34.998s
sys 0m20.554s
user + sys = 416s

Analizing results:
- I was wondering that rsync with compression faster for binary data than text data.
- With described environment I obtained huge advantage of compression-free rsync for both images.
Since rsync uses only one processor's core we can't not expect big improvement of compression speed soon.
My conclusion is that compression could be usefull for networks with speed less that 10Mb.
Since network with such a slow performance are obsolete rsync compression must be removed from code. Also this fix will allow us to decrease CPU consumption.