tailieunhanh - Tony Bourke Server Load Balancing phần 2

Local Area Network (LAN), trong khi GSLB hoạt động trên các mạng diện rộng (WAN). Có một số cách để thực hiện GSLB, chẳng hạn như DNS-based và dựa trên BGP-(Border Gateway Protocol). Có hai lý do chính để thực hiện GSLB, và để minh họa cho họ, chúng tôi sẽ sử dụng một ví dụ của GLSB trong hành động. | 10 Chapter 1 Introduction to Server Load Balancing Local Area Network LAN while GSLB works on the Wide Area Network WAN . There are several ways to implement GSLB such as DNS-based and BGP-based Border Gateway Protocol . There are two main reasons to implement GSLB and to illustrate them we ll use an example of GLSB in action. Let s take the example of a site that has a presence in two different data centers one in San Jose California and one in New York City see Figure 1-5 1. GSLB brings content closer to the users. With cross-country latency at around 60 ms milliseconds or more it makes sense to bring the users as close to the servers as possible. For instance it would make sense to send a user in North Carolina to a server in New York City rather than to a server in San Jose California. 2. GSLB provides redundancy in case any site fails. There are many reasons why an entire data-center installation can go offline such as a fiber cut a power outage an equipment failure or a meteor from outer space as every summer New York City gets destroyed in some climactic scene in a Hollywood blockbuster . Sites choosing not to put all their eggs in one basket can use GSLB technology to divert traffic to any remaining sites in case of site failures. Global Server Load Balancer San Jose Global Server I Load Balancer NYC Server Farm and Implementation Server Farm and SLB Implementation Figure 1-5. A GSLB example GSLB as a technology is still a work in progress and there are limitations to both the DNS and BGP-based methods. With DNS-based GSLB the way it is there is no guarantee that all of the West Coast users will be directed to the West Coast or all of the East Coast users will be directed to the Easts Coast and that everyone will be directed to another site in the event of a site-wide failure. There are also state and persistence issues with the various fail-over methods. Vendors are currently Other Technologies 11 working on solutions. Though not 100 percent effective