Re: [load balancing] software vs appliances.

From: Alex Samonte (asamonteIZZATsitesmith.com)
Date: Thu Feb 22 2001 - 13:38:07 EST

  • Next message: Robert Altomare: "RE: [load balancing] software vs appliances."

    On Thu, Feb 22, 2001 at 03:44:44AM -0500, tc lewis wrote:
    >
    > i've been spying on this list for a few weeks now. lots of talk about
    > foundry and alteon and cisco and such.
    >
    > anyone use software-based/os-level balancing instead of hardware
    > appliances? thoughts?

    Well, some basic drawbacks of software/os level load balancing.

    Each server must now do additional work to make load balancing happen.
    The load balancing code adds additional complexity to the site.

    These first two drawbacks go against the tried and true method of
    KISS (Keep It Simple, Stupid).

    Lastly, without a central box to handle all the scheduling the load
    balancing you do becomes MUCH less granular.

    With a central load balancer, let's say I have 10 boxes.
    If one box fails, I lose 1/10th of my capacity right? that 10th
    is distributed evenly among the remaining 9 boxes so each box handles
    1/9th the load.

    Without a central load balancer, instead using some OS level based something.
    Most of them just do IP address failovers. (I know resonate has a central
    scheduler). So when 1 box fails, some other box takes over it's IP.
    8 of the 9 boxes are doing 1/10th of the traffic, the box that took over the
    failed IP is doing 2/10ths (or 1/5th) of the traffic.

    In the case of 10 boxes it's not that bad, but if you only have 4, or 3
    boxes, you better make sure that none of them are running over 50%.

    With 10 boxes I can run each box near 90% capacity and still be able
    to handle a failover.

    -Alex



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