Re: [Bacula-users] Rate limiting in bacula?

Hi,

On Wed, 09 Dec 2009, Gabriel - IP Guys wrote:

> Is it possible to rate limit how fast a backup is sent to the SD? I have
> three collocated boxes, and they all send data at about 100m/s! We're on
> a 20 meg line, so you can imagine what happens to the rest of our
> internet abilities when the backups are running. Any ideas on how to
> slow things down to a manageable pace?

I'm not sure if Bacula has such a facility (I haven't noticed one), but
a couple of options spring to mind:

1. If you have a firewall in between, can you throttle transfers on tcp
   port 9103?

2. If your FD runs linux, you could load and use the tcp_lp congestion
   control module.  I haven't tested it particularly but the principal is
   that it works as a "bandwidth scavenger".  It works out the minimum
   round trip time on a link and wherever it sees the real RTT go higher
   than that (indicating congestion) it backs off the congestion window,
   which slows down the transfer to relieve the congestion.  Any other
   connection which needs the link should "win" the bandwidth in that
   instance.

        gavinmc@ceartgoleor:~$ modinfo 
/lib/modules/2.6.31-16-generic/kernel/net/ipv4/tcp_lp.ko 
        filename:       /lib/modules/2.6.31-16-generic/kernel/net/ipv4/tcp_lp.ko
        description:    TCP Low Priority
        license:        GPL
        author:         Wong Hoi Sing Edison, Hung Hing Lun Mike
        srcversion:     8BFC408F81AB96C2D21A317
        depends:        
        vermagic:       2.6.31-16-generic SMP mod_unload modversions 586 

3. There are other tricks you can play such as trickle:
        http://www.tuxradar.com/content/control-your-bandwidth-trickle
   I guess you could put that in the init script for either the SD or FD,
   though it would affect all transfers for that instance which might not
   be what you want.

Gavin


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