On 04/03/2014 03:35 PM, Christoph Biedl wrote:
Joe wrote...
This is way beyond my level of expertise, but wouldn't something like
ionice help with that?
Although I'm not Marian, probably not. The ionice program does a
reasonable good job when it's about prioritizing read operation. The
context makes me guess it's rather about writing.
We were using ionice and it did not help. The problem is that if for some reason all of your concurrent rsyncs are
running with the same ionice level and class, even thou they are ioniced, effectively there is no change.
So at that point we wrote a simple perl daemon that monitored rsyncs and changed ionice levels based on the amount of
time each rsync spent in each level.
We pushed all new rsyncs onto the lowest level and dynamically moved them to the top. It simply does not work as well as
I imagined.
The best solution was to use the bklio control-group, BUT, with it the backups were still slower then with the slow-down
option.
Marian
Also, check out:
2 more pipe utilities
Viewer & throttle
http://www.ivarch.com/programs/pv.shtml
Throttle - limits bandwidth of a pipe - for use with network transfers
http://linux.die.net/man/1/throttle
The pv utility is way to little known and served me well in many
situations, and throttle seems to do quite the same. Both however seem
to do quite the same thing rsync's --bwlimit option does, while the
latter is more sophisticated.
It the issue is the one I have in mind (which is one I constantly
suffer from), the actual problem is the dirty buffer writeback
strategy, deep in the Linux kernel.
Christoph
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