Linux Virtual Server
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Linux Virtual Server is a high-performance and highly scalable server built on a cluster of real servers. The architecture of the cluster is transparent to end-users. End users only see a single virtual server. The front-end before the real servers is a load balancer, which schedules requests to the different servers and make parallel services of the cluster to appear as a virtual service on a single IP address. Linux Virtual Server is added as a patch to the Linux Kernel. Modifications and additions are made to the existing kernek source to bring about Virtual Server functionalities. Mainly, the IP masquerading functionality is being modified to implement the Virtual Server support. The LVS handles connections from clients and passes them onto the real servers (so-called Layer 4 switching) and can virtualized almost any TCP or UDP service. It uses NAT (Network Address Translation) to achieve IP level load balancing. Round robin scheduling algorithm is used. Transparently adding or removing a node in the cluster achieves scalability.
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Virtual server is a highly scalable and highly available server built  on a cluster of real servers. The architecture of server cluster is fully transparent to end users, and the users interact with the cluster system as if it were only a single high-performance virtual server.
The real servers and the load balancers may be interconnected by either high-speed LAN or by geographically dispersed WAN. The load balancers can dispatch requests to the different servers and make parallel services of the cluster to appear as a virtual service on a single IP address, and request dispatching can use IP load balancing technologies or application-level load balancing technologies. Scalability of the system is achieved by transparently adding or removing nodes in the cluster. High availability is provided by detecting node or daemon failures and reconfiguring the system appropriately.
The basic goal of the Linux Virtual Server Project is to:
Build a high-performance and highly available server for Linux using clustering technology, which provides good scalability, reliability and serviceability.
The LVS cluster system is also known as load balancing server cluster.
NEED OF LINUX VIRTUAL SERVER
With the explosive growth of the Internet and its increasingly important role in our lives, the traffic on the Internet is increasing dramatically, which has been growing at over 100% annual rate. The workload on the servers is increasing rapidly so that servers will be easily overloaded for a short time, especially for a popular web site. To overcome the overloading problem of the servers, there are two solutions. One is the single server solution, i.e. to upgrade the server to a higher performance server, but it will soon be overloaded when requests increases so that we have to upgrade it again, the upgrading process is complex and the cost is high. The other is the multiple server solution, i.e. to build a scalable network service system on a cluster of servers. When load increases, we can simply add a new server or more into cluster to meet the increasing requests, and commodity server is of highest performance/cost ratio. Therefore, it is more scalable and more cost-effective to build server cluster system for network services.
METHODS TO CONSTRUCT CLUSTER OF SERVICES
There are basically two methods of constructing the cluster of services and they are:
DNS based Load Balancing Cluster
DISPATCHER based Load Balancing Cluster
DNS BASED LOAD BALANCING CLUSTER
DNS load balancing is probably the simplest method to build network service cluster. It uses Domain Name System to distribute requests to different servers through resolving the domain
Name to different IP addresses of servers. When a DNS request comes to the DNS server to resolve the domain name, the DNS server gives out one of server IP addresses based on scheduling strategies, such as in round-robin manner, then subsequent requests from clients using the same local caching name server are sent to the same server in the specified time-to-live (TTL) of name resolving.
However, due to the caching nature of clients and hierarchical DNS system, it easily leads to dynamic load imbalance among the servers, thus it is not easy for a server to handle its peak load. The TTL value of a name mapping can't be well chosen at the DNS server, with small values DNS traffic is high and DNS server will be a bottleneck, and with high values the dynamic load imbalance will get even worse. Even the TTL value is set with zero, the scheduling granularity is per host, different users' access pattern may lead to dynamic load imbalance, because some people may pull lots of pages from the site, and others may just surf a few pages and go away. Moreover, it is not so reliable, when a server node fails, the clients who map the name to the IP address will find the server is down, and the problem still exists even if they press "reload" or "refresh" button in their browsers.
DISPATCHER BASED LOAD BALANCING CLUSTER
Dispatcher, also known as load balancer, can be used to distribute load among servers in a cluster, so that the parallel services of servers can appear as a virtual service on a single IP
address, and end users interact as if it were a single server without knowing all servers in clusters. Compared to DNS based load balancing, dispatcher can schedule requests at fine granularity, such as per connection, for better load balancing among servers. Failure can be masked when one server or more fail. Server management is becoming easy, and administrator can take a server or more in and out of service at any time, which won't interrupt services to end users.
Load balancing can be done in two levels, application-level and IP-level. For example, Reverse-proxy and pWEB is an application-level load balancing method to build a scalable web server. They forward the HTTP request to the different web servers in the cluster, get back the result, and then return it to the clients. Since the overhead of dealing the HTTP requests and replies in the application-level is high, I believe the application-level load balancer will be a new bottleneck when the number of server nodes increase to 5 or more, which depends on the throughput of each server.
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With the explosive growth of the Internet, Internet servers must cope with greater demands than ever. The potential number of clients that a server must support has dramatically increased, some hot sites have already received hundreds of thousands of simultaneous client connections. With the increasing number of users and the increasing workload, companies often worry about how their systems grow over time. Furthermore, rapid response and 24x7 availability are mandatory requirements for the mission-critical business applications, as sites compete for offering users the best access experience. Therefore, the requirements for hardware and software solution to support highly scalable and highly available services can be summarized as follows:
Scalability, when the load offered to the service increases, system can be scaled to meet the requirement.
24x7 availability, the service as a whole must be available 24x7, despite of transient partial hardware and software failures.
Manageability, although the whole system may be physically large, it should be easy to manage.
Cost-effectiveness, the whole system must be economical to afford and expand.
A single server is usually not sufficient to handle this aggressively increasing load. The server upgrading process is complex, and the server is a single point of failure. The higher end the server is upgraded to, the much higher cost we have to pay.
Clusters of servers, connected by a fast network, are emerging as a viable architecture for building highly scalable and highly available services. This type of loosely coupled architecture is more scalable, more cost effective and more reliable than a tightly coupled multiprocessor system. However, a number of challenges must be addressed to make a cluster of servers function effectively for scalable network services. Linux Virtual Server is our solution to the requirements. Linux Virtual Server is a software tool that directs network connections to multiple servers that share their workload, which can be used to build highly scalable and highly available services. Prototypes of Linux Virtual Server have already been used to build many sites of heavy load on the Internet, such as Linux portal linux.com, sourceforge.net and UK National JANET Web Cache Services.
Linux Virtual Server directs network connections to the different servers according to scheduling algorithms and makes parallel services of the cluster to appear as a virtual service on a single IP address. Client applications interact with the cluster as if it were a single server. The clients are not affected by interaction with the cluster and do not need modification. Scalability is achieved by transparently adding or removing a node in the cluster. High availability is provided by detecting node or daemon failures and reconfiguring the system appropriately.
1.2 Company Profile
Since the inception in 1999, IPSR has been focusing on quality and consistency which proved to be a forerunner to our success in various spectrum of IT ranging from software application development, Networking & technical infrastructure consultancy & support to high-end IT training and certification services.
IPSR Group now stands out to be one of the leading IT concerns in Kerala and its goodwill is now noted at national level, primarily because behind the venture is a set of prominent Academicians and Industrialists with real commitment.IPSR group is headquartered at Kottayam and now belongs to the distinct class of total IT solutions Provider with its prominent presence in diversified areas of IT.
Training & Corporate Services Division
IPSR is offering training and certification in various networking courses.
RHCE (Red Hat Certified Engineer)
RHCSS (Red Hat Certified Security Specialist)
RHCDS (Red Hat Certified Data center Specialist)
RHCVA (Red Hat Certified Virtualization Administrator)
RHCA (Red Hat Certified Architect)
CCNA (Cisco Certified Network Associate)
CCNP (Cisco Certified Network Professional)
CCVP (Cisco Certified Voice Professional)
CCIE (Cisco Certified Internetwork Expert)
MCP (Microsoft Certified Professional)
MCSA (Microsoft Certified Systems Administrator)
MCSE (Microsoft Certified Systems Engineer)
MCTS (Microsoft Certified Technology Specialist)
MCITP (Microsoft Certified Information Technology Professional)
IPSR is now the only institution in India offering the top rated Certifications, RHCA & CCIE
Our training services are also offered in the following software courses
• PHP and MySQL training
• Advanced PHP training
• C# and ASP.NET (2008) training
• Java & J2 EE training
IPSR also offers Live Academic project and implimentations for students of various IT branches
IPSR is now in a possession with one of the most successful Linux division in India capable of taking up, implementing and administering corporate level Linux activities that mainly include Corporate training and Linux Server Installation and Maintenance Support.
IPSR IT Finishing School
IPSR IT finishing school is a concept aimed at moulding out truly employable candidates out of students. The new venture of IPSR is an academic-industry association, where a student is provided with training in all the needed hot skills and soft skills and then offered a real time industry experience. We have also set up an Open Source Based Development Centre (OSBDC) at Kochi for undertaking project and implimentations in Open Source technologies. Students are provided an opportunity to associate with the project and implimentations at OSBDC.
International Centre @ Kochi
IPSR was successful in setting up an international centre at Kochi mainly to offer high level certifications in Red Hat Linux. IPSR is also promoting educational tourism packages in association with the international centre to attract students from abroad.
IPSR Career Centre
Career Center is a new venture initiated by IPSR to provide placement assistance to the aspiring students in the field of Information Technology. The key objective of Career centre is to help IT students in their job-hunt and to inform them on prospective job openings. Students are offered career guidance as per the latest trends and the service also includes free job alerts directly send to the candidates as e-mails. All these services are totally free for all students. More than 2 lakh students are enrolled with ipsr career centre and our association with more than 1000 companies have helped us in catering to the students’ placement needs.
Based on our unmatched expertise in dealing with students of various profiles for the past one decade, IPSR has come up with a series of publication for IT and non IT students. The main aim of our publication division is to publish books that are specific for diverse profiles and to make them available for the entire student community at affordable rates.
Tie-ups with professional Colleges
To offer quality training and associated services, IPSR is presently associating with various leading professional colleges in Kerala. The tie up is generating fruitful results by virtue of a real-time academic industry interaction.
Achievements of Training Division:
IPSR training division is presently engaged in offering Projects, training and certification in Windows, Linux & CISCO platforms. We could also achieve several milestones in the field of Linux training in India
• Winner of Red Hat GLS National Awards for the years 2004, 2005, 2006, 2007 & 2008.
• Winner of prestigious Red Hat Asia Pacific International Award 2008 & 2009
• Produced highest number of RHCEs in the World (2500+)
• Consistent pass rate of 95 - 100% in RHCE exams
• 1 out of 20 RHCEs in the world is from IPSR
• 1 out of 6 RHCSSs in South Asia is from IPSR
• Provided corporate consultancy for many organizations
• Launched an exclusive division for foreign students and NRIs
• Produced the World’s youngest & second Youngest RHCEs
Software Development Division
The company has developed a host of software products with a very large client base. The main products include
• eZcom, a complete accounting package
• iCMS a web-content management software
• Quicksite, an easy way to build dynamic websites
• Custom package implementation for CRM, SCM solutions
• E-business solutions
• The company has developed portals and sites for almost 1000 business concerns across Kerala. Kerala Web Directory is a portal developed and maintained by IPSR.
Overseas Development Division
ipsr sololutions ltd. has an Overseas Development Division that concentrates exclusively on Overseas Projects. Most of the overseas project and implimentations undertaken are Open Source based and the division is currently operating from Kochi.
Hardware & Networking Solutions
The e company has a strong computer hardware & networking Solutions division with almost 2500 customers.
As part of corporate social responsibility, IPSR is now into a lot of social project and implimentations as well. Some of the initiatives include
Talent genie Programme : This programme envisions to find out real talents from the campus and to offer placement assistance to them. The selected candidates are also offered handsome gifs and other privileges.
Teen Cyber Project : This project and implimentation is aimed at identifying children who demonstrate high level of interest for Information technology. Selected children are given free training programmes so as to groom them to become productive professionals and entrepreneurs.
Scholarship Programme : Various scholarship programmes are also offered for the deserving students to aid their formal learning.
1.3 Architecture Diagrams
1.4.1 What is clustering?
Clustering is the use of multiple computers, typically PCs or UNIX workstations, multiple storage devices, and redundant interconnections, to form what appears to users as a single highly available system. Cluster computing can be used for load balancing as well as for high availability. It is used as a relatively low-cost form of parallel processing machine for scientific and other applications that lend themselves to parallel operations.
Computer cluster technology puts clusters of systems together to provide better system reliability and performance. Cluster server systems connect a group of servers together in order to jointly provide processing service for the clients in the network.
Cluster can offer,
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18-07-2011, 10:17 PM
can anyone mail me its ppt presentation ..pls..
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19-07-2011, 09:40 AM
you can refer these page details of "Linux Virtual Server"link bellow
please read topicideashow-to-linux-virtual-server for getting report and more information of linux virtual server
and read topicideashow-to-virtual-network-computing-full-report its a related topic virtual computing