Summary: Network Load Balancing

From: April Sims (
Date: Wed May 17 2000 - 16:12:36 CDT

>Original question:
> > Looking to purchase some hardware. The choice is between a single E450 vs.
> > using dual E250's for the same Web-based portal application that
> > authenticates and authorizes users that logon- Netscape Web server w/
> > LDAP, Gemstone JavaDB.
> >
> > The theory is that (using the dual E250's) if we put DNS round robin for IP
> > requests, mirror the drives (with their own 100Mb dedicated pipe between
> > them) we can outperform a single E450 as well as never be down for backups
> > or failover. Disconnect the mirror, backup, reconnect.
> >
> > Is there any problem with this scenario? Am I on a wild hare? Thanks.

Responses: Thanks to Jeff Kennedy, Lee Trujillo, Michael Salehi, Robert
Hayne, Erin Jones, Rick Fincher,
Mark Scarborough and Joe Thykattil and anyone that is going to respond
after I send this summary.

Everyone was positive except for the DNS round-robin scenario that is a
manual failover. I agree to that statement and plan to look into software
or hardware implementation for true fail-over capability.

>The problem is the round-robin dns. If one of the servers is down, half
>of the people trying to connect will get a no response answer. This is
>because dns will give them the ip of the down server every other time.
More boxes = fewer single points of failure

So, I'd agree with the 2 E250's as long as you can really load balance
between them.
Round-robin DNS is OK to a point but it can easily overload one server
while the other is

Anyway, the only real reason I replied is to say "Hey" - I'm an ACU grad,
class of '86 -
Computer Science...

Good luck on your project.


Sounds like a good plan. Although the 450 can be configured with two power
supplies, and you can do almost anything but hot swap processors and memory
need the 3500 or > for that), two redundant machines will be more flexible and
give you better uptime.

Performance will probably not be faster though because the bottleneck is going
to be the speed of the mirroring link.

If you can afford it you can use fiber channel drives that the two boxes can
share (faster than 100 mbs but $$$) to give better performance in a setup like
this. That would eliminate the overhead of mirroring, but then you would be
to a single system (the fiber channel drive unit) being a failure point
that can
take you down.

If you use a raid array that possibility is reduced though.

Hope this helps.

Best Regards,

Rick Fincher
I would do the 2 250's. we have 2 450's running our front end I really like
it. I would suggest a load balancer app though. I like f5's bigIP. if you
just round robin the dns you will still get failures if one of them is down.
the bigIP (besides providing an extra layer of security) intelligently
routes the traffic as per a couple of different algorithms.
best part is you can do upgrades and such to one while the other is still
running. not only does this mean no downtime but if something doesn't work
you can back out more easily. if the machines are identical they are hot
backups of each other as well. (though a tape backup is still a good idea

as far as performance, it would obviously depend on the hardware you choose
for each. having said that, 2 machines would almost have to out perform the
one. much more I/O available and half the traffic on the bus.

You are on the right track there.

Robert Hayne
You should be fine. As long as your web pages are read only.

Mike Mehran Salehi

April Sims MCSE, CNE Abilene Christian University
Systems Administrator ACU Box 29005
Information Technology Abilene, TX 79699 Vx:(915)674-2681 Fx:674-6724

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