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
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
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
On 14-Mar-2008, at 12:42, Joe Shen wrote:
Is there any way to solve problem above?
would probably work, so long as the routers choosing between the ECMP routes are able to make route selections per flow, and not just
The approach described in <http://www.nanog.org/mtg-0505/abley.cluster.html 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
On 14-Mar-2008, at 12:42, Joe Shen wrote:
Is there any way to solve problem above?
would probably work, so long as the routers choosing between the ECMP routes are able to make route selections per flow, and not just
The approach described in <http://www.nanog.org/mtg-0505/abley.cluster.html 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
On Sat, 15 Mar 2008 00:42:26 +0800 (CST) Joe Shen <joe_hznm@yahoo.com.sg> 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"
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@merit.edu [mailto:owner-nanog@merit.edu]On Behalf Of Mark Smith Sent: Friday, March 14, 2008 6:44 PM To: Joe Shen Cc: lb-l@vegan.net; 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@yahoo.com.sg> 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"
participants (7)
-
Bill Nash -
Darden, Patrick S. -
Joe Abley -
Joe Shen -
John Moser -
Larry J. Blunk -
Mark Smith