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On Tue, Feb 28, 2012 at 4:18 AM, Simon Horman <horms@xxxxxxxxxxxx> wrote:
> On Mon, Feb 27, 2012 at 10:32:16AM -0500, Khosrow Ebrahimpour wrote:
> > Hi Krishna,
> >
> > On Monday, February 27, 2012 08:08:13 am krishna prasad wrote:
> > > Dear All,
> > > If the director is configured with Source Hashing scheduling
> algorithm,
> > > the connections are distributed among the back end real servers through
> > > looking up a statically assigned hash table by their source IP
> addresses.
> > > My question here is the key for the load balancing is the source IP
> alone
> > > or source IP plus port?
> >
> > I haven't used SH scheduling myself, but according to this article
> > http://kb.linuxvirtualserver.org/wiki/Source_Hashing_Scheduling only the
> > source IP is used.
>
> Yes, the SH scheduler only makes use of the source IP address and
> conversely the DH scheduler only makes use of the destination IP address.
>
> > Although I am curious why the hash wouldn't use source IP + Port.
> Otherwise,
> > clients coming from behind a NAT or proxy will all end up on the same
> > realserver.
>
> I believe that the motivation for the DH scheduler was for use with
> load-balanced caching proxy servers. The SH scheduler is intended
> to be used in place of persistence in some situations where it is
> desirable to scheduler the same client to the same real-server.
>
> Clearly the presence of NAT can potentially result in a poor result
> when using SH. Likewise with persistence, which can provide some
> of the same behaviour.
>
> With regards to SH hashing on both the Source IP and port, I'm unclear
> of when this would be useful in place of for example WLC
>
> I agree that the original motivations of SH (and DH) may not needed to
> have IP+port hash;
>
But I strongly think that it it good to have IP+port hashing, for cases
where multiple clients run on single host, in this case
the connections have same IP but different port. In this case also the same
is desirable,i.e same client to the same real-server.
This may not make a real use case for web world, but a strong case for
non-web deployments like in telecom.I know LVS is increasingly used in
other than web services.
>
> _______________________________________________
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> http://www.linuxvirtualserver.org/
>
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>
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