Re: RFC: slow-down option

[Frank Terhaar-Yonkers]

I needed to back up some of my NAS over the WAN to another (friends) NAS (3/4TB-total).  A lot of expensive hi-def music files, mostly very large.  He backs up to mine, vice versa for disaster recovery. There were two issues:  1) sucking up all my UL bandwidth, only 5mbit in this case, 2) having the option to do a "delayed" kill of the rsync when it *finished* the current file rather than an immediate stop so as not to waste the bandwidth already used to move a portion of a large file. I implemented both with signals.  A signal toggles the enable/disable of the --bwlimit=XXX param so you can do a simple throttle back or run wide open.  The second signal is a delayed quit - when current file is finished. This seemed to work pretty well.  During the day when I needed the BW for work, etc.  I'd throttle it, then let it run wide open at night.  This could be expanded with a BW list, so instead of a simple toggle, the next BW setting in the list could be used, round-robin.  The delayed quit was nice if new content was added that I felt I wanted backed up first.  Quit (delayed), then restart, easily scripted. Let me know if there is any interest in putting this in the code base and I'll create some diffs for review. Cheers, Frank On 4/3/14, 10:47 AM, Marian Marinov wrote: 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 -- Frank Terhaar-Yonkers W4FTY Cisco Systems, Inc. 7025 Kit Creek Road PO Box 14987 Research Triangle Park, North Carolina 27709 f...@cisco.com voice(919)392-2101 JabberCall me browser-based video chat

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