Thanks a lot guys. For your suggestion. it really helped me a lot MOHAMMED ASHRAF
MOB: 9870161983 --- On Wed, 10/3/10, Nadeem M. Khan <[email protected]> wrote: From: Nadeem M. Khan <[email protected]> Subject: Re: [LinuxVadaPav] help on cluster server To: [email protected] Date: Wednesday, 10 March, 2010, 8:04 PM On Wed, Mar 10, 2010 at 2:21 PM, ashraf mohammed <ashraflinux@ yahoo.com> wrote: > > > > HI guys > i want to know wat is cluster server on linux .And how to configure it. and > can i do clustering of server on my home pc.i am using vmware 6.0.5. i can > add as many server as a want in vmware. So can i learn clustering at home. > i want to learn basic clustering first. so guys can u help out with some > ideas. > how to achieve this... > or any documentation which will help me in better way Hi Ashraf, I wouldn't get too much into the theory of clusters, but want to share info from a practical point of view. Clustering is used to accomplish either of two objectives - High Availability or Load Balancing. There are tons of docs for the latter so I'll leave it for you to read those up. As far as HA is concerned, the objective if to keep your resource (application or database or whatever) you want always available. The operation is like so: You have two nodes running Linux or Unix and a shared storage (either fibre channel or nfs, but fc has better performance) . For example, lets consider you have an apache webserver that you want to be highly available. For this, you would have a volume group residing on the SAN and which is shared across both nodes. This volume group will contain apache's document root and other files required for apache's operation. Each node will have at least two IP addresses. One service IP used for accessing the webserver and another private IP used to connect the two nodes for heart beat. These IPs are in different subnets.Let' s say your primary node is NodeA and secondary is NodeB. Under normal operation, when uses access your website, they will be directed to NodeA and everything will be fine. The cluster software monitors the availability of each node using the heatbeat IPs. Lets say NodeA crashes, the cluster softare will miss a few heatbeats and detect that NodeA has crashed. The service IP will then move to NodeB. Teh VG will be moved to NodeB and varied on in exclusive mode. This is termed as failover. When users access your webserver now, they will be directed to NodeB. All this is transparent to the users and they will not be aware of the failover except for the time it actually takes for the failover to complete. When you fix NodeB and bring it back up, the cluster heartbeat will detect this and move the service IP back to NodeA. The VG will be varied off on NodeB and move to NodeA. This is termed as failback. Users will be directed to NodeA now as things are back to normal. Some examples of HA clustering software: Linux: RHCS, Veritas, Linux-HA AIX: HACMP HP-UX: ServiceGuard Solaris: Veritas. Oracle DB: RAC. RAC is a bit different as it uses the concept of virtual IP (VIP) instead of service IP. This was just a simple example involving IP and VG. You basically have scripts to determine what action needs to be taken during failover and failback. It is possible to install a Linux cluster on Vmware. I remember reading a doc online but for the life of me can't recollect where. Google is your friend. Regards, NMK. Your Mail works best with the New Yahoo Optimized IE8. Get it NOW! http://downloads.yahoo.com/in/internetexplorer/ [Non-text portions of this message have been removed]
