reducing I/O and system load

[Denis Solovyov]

>>> > I'm using rsync for simple daily back up data from one HD to another. It
>>> > takes  about  10  minutes  daily  under  "nice  -n  19".  The problem is
>>>      --bwlimit=KBPS          limit I/O bandwidth; KBytes per second
MM>> --bwlimit only limits the rate of transfer over the network.  Vilius
MM>> Puidokas encountered the same problem and traced it to the scanning as
MM>> rsync generates the file list.  He wrote a patch that adds a --slow-down
MM>> option that makes rsync wait a few microseconds in between scanning each
MM>> file.  Find it here:
MM>>         http://vilius.multiply.com/video/item/10
DS> usleep(100) in that place of the source shown on the page really helps,
DS> but it dramatically increases the time of rsync'ing.  I guess Vilius'

Just for information.
Not completely sure, but it seems that making huge rsync'ed
partitions "noatime" (/etc/fstab) slightly helps as well.

I guess that 50% or so of rsync usage is disk-to-disk backup,
strange that it's impossible to find anywhere the proper
solution on how to reduce I/O load. The workaround SHOULD
be suggested by the software directly, I believe...

Best regards,
Denis Solovyov