load balancing...

[Tony S. Yuan]

You can take a look on my company's Global Dispatch,
it can do dynamic load balancing  based on latency, load
and availibities of your servers or clusters.

- Tony

Kevin Darcy wrote:

> Joseph S D Yao wrote:
>
> > On Mon, Sep 18, 2000 at 02:50:20PM -0700, arvind rao wrote:
> > >   I need to setup one domain-name for 2 IP addresses
> > > such that if one of the machines are not up, it should
> > > automatically pick the other one.
> > >   What I saw with having just 2 "A" record entries in
> > > the named.domain-name/IPnetwork file was that if I try
> > > to ping the "domain-name", it randomly picks one of
> > > the 2 IP'S and if it picks the IP address of the
> > > machine which is down, then it just doesnt
> > > automatically try the other machine. How do I set it
> > > up so that it identifies the other machine if one
> > > machine is down.
> > >   Is there a way to set priority level????
> >
> > It can't be done with just DNS and BIND.
>
> Hmm... Perhaps that's a little too absolute. SRV can do what the poster
> wants, once web clients start using it. And even today, switching an
> A record automatically in case of failure, or giving out both addresses in
> "fixed" order on all of the authoritative servers, can at least provide
> *some* degree of automatic failover capability, although perhaps only at
> the expense of making the records very volatile and, in the case of the
> "fixed order" solution, requiring a certain amount of failover smarts in
> the client and dealing with the inevitable "spillover" traffic to the
> backup server (which can possibly be handled with a web redirect or
> whatever). There aren't any *good* DNS-only solutions today, but there are
> halfway solutions. At least until SRV gets fully specified and deployed.
>
> > There are some commercial
> > products that will do this, however.
>
> Indeed. But they tend to be rather expensive. Moreover, most if not all of
> them make the A records they manage very volatile, which is one of the
> biggest drawbacks of DNS-based failover, so how is this much better than
> just scripting your own failover mechanism? I can't imagine that it would
> be that hard to write a script which senses whether the main webserver is
> down and, if it is, pokes DNS with a new A record, or deletes the main
> webserver's A record from a multi-valued  RRset, via Dynamic Update, and,
> optionally, tells the backup webserver to turn off its redirect.
>
> Dynamic Load Balancing, on the other hand, can get a lot more complicated.
> I can see legitimate reasons for shelling out significant sums of cash for
> a box that does that task well.
>
> - Kevin