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Cluster Solution

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SlopeZ
Frequent Advisor

Cluster Solution

Hi all,

i'm planning to start a new arquitecture of a project about web and application servers.

Functional components:
RHEL 3.0
1 apache web server
1 tomcat web server
1 bbdd oracle

I have 3 physical servers and i'd like to use 2 of them for web-app layer and the other one to bbdd layer.

Apache y Tomcat software are in the same server; i'd like to put in LB and cluster. Both connects to the other server to bbdd.

The configuration i want is active-active: apache and tomcat in both server to balance the load, and if one of the servers fails the service go on.

I'm thinking about Cluster Suite, but what hardware i need for this purpose?
Do i need another server in the front of cluster nodes to Load Balance?


I haven't a shared disk array for the cluster but i can use Rsync software to synchronize data between the 2 nodes. ¿it's this posible?
i know that isn't the best performance option.


Can you give me any ideas?

Thanks a lot!
10 REPLIES
Steven E. Protter
Exalted Contributor

Re: Cluster Solution

Shalom,

HP has a cluster you can order with shared storage that should work right out of the box. You can go active active. It ships with a fiber switch and is very, very reliable.

The shared storage is an MSA-1000, which is affordable and reliable as well.

http://h18004.www1.hp.com/products/servers/platforms/index-dl.html

There are pre-built clusters that are guaranteed to work. I won't tell you there is no configuration, becasue there is, but you can buy a proven solution.

SEP
Steven E Protter
Owner of ISN Corporation
http://isnamerica.com
http://hpuxconsulting.com
Sponsor: http://hpux.ws
Twitter: http://twitter.com/hpuxlinux
Founder http://newdatacloud.com
SlopeZ
Frequent Advisor

Re: Cluster Solution

Thanks SEP for the reference,
but the hardware is bought now.

I must use the proliants that i have.

Regards!
Ivan Ferreira
Honored Contributor

Re: Cluster Solution

You could use a simple DNS round robin for load balance, but if you want a real load balancer, you need a two tier configuration, for use with Red Hat Cluster (Piranha) or Linux LVS. Also, this load balancer should be redundant, so you need two servers.

For the failover you can use heartbeat and also Red Hat Cluster Manager. And yes, you can use rsync to sync the data or have the data on a good NFS server or NAS.
Por que hacerlo dificil si es posible hacerlo facil? - Why do it the hard way, when you can do it the easy way?
Vitaly Karasik_1
Honored Contributor

Re: Cluster Solution

These articles may be useful for you:

These are nice articles in Linux Magazine about clustering:
http://www.linux-mag.com/2003-11/clusters_01.html Linux Virtual Server Clusters

http://www.linux-mag.com/2003-11/availability_01.html Highly-Affordable High Availability

http://www.linux-mag.com/2003-11/drbd_01.html Data Redundancy By DRBD [DRBD is (http://www.drbd.org/) " a block device which is designed to build high availability clusters. This is done by mirroring a whole block device via (a dedicated) network. You could see it as a network raid-1."]

Rgds,
Vitaly
SlopeZ
Frequent Advisor

Re: Cluster Solution

Hi Ivan,

i'm reading about LVS for Load B. I have de Cluster Suite software but i don't know how implement the best solution.

In LVS, do you know if the LVS Routers are physical machines or its a service installed in the clustered nodes?

Have you got any 'how to' install it?

In other way, de DNS Round Robin for a www.mydomain.com must be implemented in my domain name host supplier, isn't? (i.e. public dns servers around the internet..)

Thanks in advance.

Regards!
Ivan Ferreira
Honored Contributor
Solution

Re: Cluster Solution

The LVS routers are physical machines (usually 2) that runs a set of services to provide load balancing and high availability.

Behind these machines are the real servers that runs the services that you want to be accesible by the clients. It's a two tier configuration.

For detailed information about the cluster and the configuration see the Red Hat Cluster Suite "Configuring and Managing a cluster" documentation available at:

http://www.redhat.com/docs/manuals/csgfs/

DNS round robin is configured by the person that manages the DNS server authoritative for your domain. In some cases that is your ISP, but sometimes, the client itself manages their DNS servers. If you usually don't deal with DNS servers, then probably in your case is your ISP.
Por que hacerlo dificil si es posible hacerlo facil? - Why do it the hard way, when you can do it the easy way?
Steven E. Protter
Exalted Contributor

Re: Cluster Solution

I've got a pair of old desktops running RH 4 Update 2 clustering.

The key factor there is that the shared storage requirements have been lifted.

I've found with DLM that the lack of a shared storage device is not a problem. I have the exact services you mention and a few others failing back and forth quite nicely between the nodes.

Its worth a look, because it will work with almost any hardware I've tried so far.

SEP
Steven E Protter
Owner of ISN Corporation
http://isnamerica.com
http://hpuxconsulting.com
Sponsor: http://hpux.ws
Twitter: http://twitter.com/hpuxlinux
Founder http://newdatacloud.com
SlopeZ
Frequent Advisor

Re: Cluster Solution

Ok Ivan, this post resolve my questions.

One more question:

Cluster Suite has two functionalities:
- high availability (cluster services)
- load balancing

If i want the two servers nodes with the same services up and running, and only balance the web requests, i only need load balancing, it's right?
or need i install the cluster package too?



SEP: i guess that you have and active-active configuration with the services distribuited in the nodes... it's ok?
The other configuration that you can have it's active-pasive with the same services in the nodes, it's ok?

Regards!
Thanks in advance.
Steven E. Protter
Exalted Contributor

Re: Cluster Solution

Hi,

I currently have an active passive configuration with services running on one node or the other.

The pirhana package with LVS can be used to set up a load balancing router that is active active.

No shared storage required.

I'm not totally confident in the LVS Pirhana configuration on how it will deal with one node being offline. The diagrams show a more complex setup with two nodes acting as a router, pushing traffic to a series of application servers behind the two routers.

I chose my configuration because it mimics my companies current production cluter configuration. I'm going to test other configurations as well.

My understanding is that for load balancing to work, the clustering rpms must be installed and running as well. The documentation such that it is hardly makes that very clear though.

When I have enough machines, I'll run a test and confirm it all.

Next for my cluster is a sendmail cluster that receives all mail on a floating IP address and an active-passive oracle cluster mimicing more of my companies production configuration.

Clustering is fun, even at a point a post. :-)

Seriously, I hope I helped and would be happy to share information with you and review configuration files.

SEP
Steven E Protter
Owner of ISN Corporation
http://isnamerica.com
http://hpuxconsulting.com
Sponsor: http://hpux.ws
Twitter: http://twitter.com/hpuxlinux
Founder http://newdatacloud.com
Ivan Ferreira
Honored Contributor

Re: Cluster Solution

Yes, you only need load balancing, the nodes where the cluster suite is installed will be the Director (first layer).

clients-----directors----real_servers

Behind these servers, will be the "real servers" that will run the same service (web service). This is the second layer. The Director will then re-route the request to the real servers. The real servers does not requiere the cluster suite software.
Por que hacerlo dificil si es posible hacerlo facil? - Why do it the hard way, when you can do it the easy way?