Re: [BackupPC-users] Backups stalling for no apparent reason

[Les M. <les...@gm...>]

Carl Wilhelm Soderstrom wrote:

>> When doing a backup, the whole thing seems to just stall for no reason.  
>> While watching top, I noticed that the system is idle and BackupPC_dump 
>> is nowhere on the list of active processes.  This will last for several 
>> minutes before it shows up again and gets back to work.  It will work 
>> for a minute or two before disappearing again.  The client is completely 
>> idle while this is going on.  Looking at the process list, I can see 
>> that the processes are still running on both servers with the same 
>> process ids.  
> 
> 
> Have you used a tool like 'iftop' to check the network traffic while this is
> going on?
> 
> Have you tried 'dstat' or 'iostat' or 'atop' or the like to see how much
> disk activity is going on at each end?
> 
> I'm not doubting you; I've seen similar behavior at times. I suspect a bug
> in some rsync implementation somewhere along the line.

During rsync full runs it is normal to have long periods when not much 
is transferred although the boxes should still be busy accessing files. 
  On incremental runs there will be similar periods but without much 
visible activity as the matching directory contents are compared and 
skipped - these should be short unless you have a very large number of 
unchanged files - or the directory size forces the server to swap.
You could try an 'strace -p' on the process to see if it is making any 
system calls.

I've heard that some of the kernel process scheduling methods can slow 
single very busy processes but I haven't tried anything but the defaults 
myself.

-- 
    Les Mikesell
     les...@gm...