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load balancing and fault tolerance without load balancer

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joe_hznm at yahoo

Mar 14, 2008, 9:42 AM

Post #1 of 7 (964 views)
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load balancing and fault tolerance without load balancer

hi,

we plan to set up a web site with two web servers.

The two servers should be under the same domain
name. Normally, web surfing load should be
distributed between the servers. when one server
fails, the other server should take all of load
automatically. When fault sever recovers, load
balancing should be achived automatically.There is no
buget for load balancer.

we plan to use DNS to balance load between the two
servers. But, it seems DNS based solution could not
direct all load to one server automatically when the
other is down.

Is there any way to solve problem above?

we use HP-UX with MC-Service Guard installed.

thanks in advance.

Joe

__________________________________________________________________
Tired of visiting multiple sites for showtimes?
Yahoo! Movies is all you need
http://sg.movies.yahoo.com

billn at billn

Mar 14, 2008, 9:48 AM

Post #2 of 7 (900 views)
Permalink

Re: load balancing and fault tolerance without load balancer [In reply to]

NANOG really isn't the forum for this kind of conversation.

That said, look into devices like Alteons, or open source solutions like
Balance-NG. Even Apache can be used for this with something like
mod_proxy. Good luck.

- billn

On Sat, 15 Mar 2008, Joe Shen wrote:

>
> hi,
>
> we plan to set up a web site with two web servers.
>
> The two servers should be under the same domain
> name. Normally, web surfing load should be
> distributed between the servers. when one server
> fails, the other server should take all of load
> automatically. When fault sever recovers, load
> balancing should be achived automatically.There is no
> buget for load balancer.
>
>
> we plan to use DNS to balance load between the two
> servers. But, it seems DNS based solution could not
> direct all load to one server automatically when the
> other is down.
>
>
> Is there any way to solve problem above?
>
> we use HP-UX with MC-Service Guard installed.
>
>
> thanks in advance.
>
> Joe
>
>
> __________________________________________________________________
> Tired of visiting multiple sites for showtimes?
> Yahoo! Movies is all you need
> http://sg.movies.yahoo.com
>

ljb at merit

Mar 14, 2008, 9:49 AM

Post #3 of 7 (898 views)
Permalink

Re: load balancing and fault tolerance without load balancer [In reply to]

You might want to consider client side load balancing --

http://www.digital-web.com/articles/client_side_load_balancing/

Joe Shen wrote:
> hi,
>
> we plan to set up a web site with two web servers.
>
> The two servers should be under the same domain
> name. Normally, web surfing load should be
> distributed between the servers. when one server
> fails, the other server should take all of load
> automatically. When fault sever recovers, load
> balancing should be achived automatically.There is no
> buget for load balancer.
>
>
> we plan to use DNS to balance load between the two
> servers. But, it seems DNS based solution could not
> direct all load to one server automatically when the
> other is down.
>
>
> Is there any way to solve problem above?
>
> we use HP-UX with MC-Service Guard installed.
>
>
> thanks in advance.
>
> Joe
>
>
>

jabley at ca

Mar 14, 2008, 10:00 AM

Post #4 of 7 (910 views)
Permalink

Re: load balancing and fault tolerance without load balancer [In reply to]

On 14-Mar-2008, at 12:42, Joe Shen wrote:

> Is there any way to solve problem above?

The approach described in <http://www.nanog.org/mtg-0505/abley.cluster.html
> would probably work, so long as the routers choosing between the
ECMP routes are able to make route selections per flow, and not just
per packet (e.g. "ip cef" on a cisco).

Tony Kapela did a lightning talk a few meetings ago about another
cisco-specific approach which used some kind of SLA-measuring cisco
feature to do the same thing without needing to run a routing protocol
on a server. I can't seem to find a link to the details, but if
someone else knows where it is it'd be good to know.

Joe

jmoser at diamondgate

Mar 14, 2008, 11:45 AM

Post #5 of 7 (901 views)
Permalink

Re: load balancing and fault tolerance without load balancer [In reply to]

>
>
> On 14-Mar-2008, at 12:42, Joe Shen wrote:
>
>> Is there any way to solve problem above?
>
> The approach described in
> <http://www.nanog.org/mtg-0505/abley.cluster.html
> > would probably work, so long as the routers choosing between the
> ECMP routes are able to make route selections per flow, and not just
> per packet (e.g. "ip cef" on a cisco).
>
> Tony Kapela did a lightning talk a few meetings ago about another
> cisco-specific approach which used some kind of SLA-measuring cisco
> feature to do the same thing without needing to run a routing protocol
> on a server. I can't seem to find a link to the details, but if
> someone else knows where it is it'd be good to know.

http://www.nanog.org/mtg-0710/presentations/Kapela-lightning.pdf

-John

nanog at 85d5b20a518b8f6864949bd940457dc124746ddc

Mar 14, 2008, 3:44 PM

Post #6 of 7 (888 views)
Permalink

Re: load balancing and fault tolerance without load balancer [In reply to]

On Sat, 15 Mar 2008 00:42:26 +0800 (CST)
Joe Shen <joe_hznm [at] yahoo> wrote:

>
> hi,
>
> we plan to set up a web site with two web servers.
>
> The two servers should be under the same domain
> name. Normally, web surfing load should be
> distributed between the servers. when one server
> fails, the other server should take all of load
> automatically. When fault sever recovers, load
> balancing should be achived automatically.There is no
> buget for load balancer.
>
>
> we plan to use DNS to balance load between the two
> servers. But, it seems DNS based solution could not
> direct all load to one server automatically when the
> other is down.
>
>
> Is there any way to solve problem above?
>

One option might be to run two instances of VRRP/CARP across the hosts.
You have Host A being the primary/master for one IP address that's in
your DNS, and Host B being the primary/master for the other IP addess
that's in your DNS. Host A is the secondary/backup for the IP address
normally owned by Host B and Host B is the secondary/backup for the IP
address normally owned by Host A. When, for example, Host A fails, Host
B takes over being the primary/master for both IP addresses in your
DNS, giving you your continued availability. If you want make that fail
over transparent to load, you'd need to keep the load on the hosts <50%
under normal, non-fail circumstances.

Regards,
Mark.

--

"Sheep are slow and tasty, and therefore must remain constantly
alert."
- Bruce Schneier, "Beyond Fear"

darden at armc

Mar 17, 2008, 5:29 AM

Post #7 of 7 (900 views)
Permalink

RE: load balancing and fault tolerance without load balancer [In reply to]

I understand you have no budget for a comercial load balancer; however, you should consider setting up two inexpensive servers or PCs as load balancers. You could do it with one, but that would itself be a single point of failure. The OS and software are all free. Two old PCs would be next to free. Heck, two bottom of the line new servers would only cost $2K--$3K total.

OS linux (fedora 8, SUSE, any modern distro)
Software LVS ( http://www.linuxvirtualserver.org/ )
HA ( http://www.linux-ha.org/ )

The How To documentation is short and sweet (there is a full how to, and a mini how to) http://www.austintek.com/LVS/LVS-HOWTO/ . I've been running a cluster of 12 web servers for almost 5 9s for 6 years now based off this stuff. You can take a server down for maintenance and nobody notices.

There is a complete bundled package using RPM called Ultra Monkey--it includes LVS and HA and everything else you need. Find it here: http://www.ultramonkey.org/ Documentation that should work for Fedora, CentOS, and RHEL4+ is at http://www.jedi.com/obiwan/technology/ultramonkey-rhel4.html

--p

-----Original Message-----
From: owner-nanog [at] merit [mailto:owner-nanog [at] merit]On Behalf Of
Mark Smith
Sent: Friday, March 14, 2008 6:44 PM
To: Joe Shen
Cc: lb-l [at] vegan; NANGO
Subject: Re: load balancing and fault tolerance without load balancer

On Sat, 15 Mar 2008 00:42:26 +0800 (CST)
Joe Shen <joe_hznm [at] yahoo> wrote:

>
> hi,
>
> we plan to set up a web site with two web servers.
>
> The two servers should be under the same domain
> name. Normally, web surfing load should be
> distributed between the servers. when one server
> fails, the other server should take all of load
> automatically. When fault sever recovers, load
> balancing should be achived automatically.There is no
> buget for load balancer.
>
>
> we plan to use DNS to balance load between the two
> servers. But, it seems DNS based solution could not
> direct all load to one server automatically when the
> other is down.
>
>
> Is there any way to solve problem above?
>

One option might be to run two instances of VRRP/CARP across the hosts.
You have Host A being the primary/master for one IP address that's in
your DNS, and Host B being the primary/master for the other IP addess
that's in your DNS. Host A is the secondary/backup for the IP address
normally owned by Host B and Host B is the secondary/backup for the IP
address normally owned by Host A. When, for example, Host A fails, Host
B takes over being the primary/master for both IP addresses in your
DNS, giving you your continued availability. If you want make that fail
over transparent to load, you'd need to keep the load on the hosts <50%
under normal, non-fail circumstances.

Regards,
Mark.

--

"Sheep are slow and tasty, and therefore must remain constantly
alert."
- Bruce Schneier, "Beyond Fear"

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