Nice to have features

[Markus Bernhardt <mbernhardt@xxxxxxxxxx>]

I have been evaluating most of the existing load balancing solutions.
To make it short:
If you want buying it in hardware DON'T take CISCO Local Director,
which
is that bad you won't believe. The best solution in hardware I
have found are
the machines produced by Alteon Web Systems.
But the best approach for load balancing is LVS. Its a flexible
software,
and its open source.

I also found some nice features which should be implemented in the future.

1. Load Balancing based upon a hash calculated from src-ip and dest-ip.

    I know that does not sound very nice, but it is needed, if you want to load
    balance firewalls. Load Balancing firewalls means, that you need 2 directors.
    One in the dirty and one in the clean segment. The problem is, that both
    directors have to choose the same firewall(realserver) for a package going
    from outside to inside and vice versa. Because (at the moment) the one director
    does not know anything about the other, you have to balance the traffic by
    the things, which are for both the same, the src-ip and dest-ip.

2. Load balancing based upon URL
 
    Think about the content of a big internet site. It has html, cgi, gif,
    video-streams, mp3 ...
    Lets say you need 10 servers. Using normal load balancing means you have
    to buy 10 quite big == expensive machines. Now it could be economical
    interresting to divide things up.
    Example:
        2 big machines, which are holding the whole content
        4 machines, which are holding streaming media. This machines don't need
          to be that powerfull (CPU). They only have to have a big I/O-system.
        4 machines for cgi etc. They need much CPU and Memory, but only an small
          I/O-system.

        Konfiguration:
            Groups:
                Group        Machine        Load Balancing Type
                  1          1,2            lc
                  2          3,4,5,6        wlc
                  3          7,8,9,10       rr

            Rules:
                Rule         Group
                .gif           2
                .mp3           2
                .cgi           3
                .exe           3
                <any>          1

3. active/active Configuration of the directors

    If you setup a redundant lvs you have a active director and an sleeping passive
    director. But mostly you will also have redundant uplinks. Following
    situation would be nice.
    Both directors are active and are connected to both uplinks. If both are working
    each of them is using one uplink exclusive. If one director fails, the other
    director should use both uplinks, if an uplink fails both directors sould use the
    remaining one. Perhaps VRRP between the directors would be useful.
 
 
 

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