1 00:00:00,120 --> 00:00:02,250 ‫Okay, so let's summarize the section 2 00:00:02,250 --> 00:00:04,410 ‫on the ELB and the ASG. 3 00:00:04,410 --> 00:00:07,860 ‫So first, we discussed the concept of high availability. 4 00:00:07,860 --> 00:00:10,560 ‫Scalability would be vertical and horizontal, 5 00:00:10,560 --> 00:00:13,380 ‫elasticity and agility in the Cloud. 6 00:00:13,380 --> 00:00:15,690 ‫It is very important for you to understand 7 00:00:15,690 --> 00:00:18,780 ‫to which concept corresponds to which features. 8 00:00:18,780 --> 00:00:20,340 ‫For example, high availability 9 00:00:20,340 --> 00:00:22,410 ‫means that you are having your applications 10 00:00:22,410 --> 00:00:24,870 ‫across multiple availability zone. 11 00:00:24,870 --> 00:00:27,060 ‫Vertical scaling means that you're increasing the size 12 00:00:27,060 --> 00:00:28,020 ‫of an instance. 13 00:00:28,020 --> 00:00:29,310 ‫And horizontal scaling, 14 00:00:29,310 --> 00:00:32,400 ‫is that you are increasing the number of instances. 15 00:00:32,400 --> 00:00:35,580 ‫Elasticity is the ability to scale up and down 16 00:00:35,580 --> 00:00:36,630 ‫based on demand. 17 00:00:36,630 --> 00:00:39,630 ‫And agility is a concept of the Cloud that is going 18 00:00:39,630 --> 00:00:41,460 ‫to be able to make you work faster, 19 00:00:41,460 --> 00:00:43,260 ‫because you can create and delete resources 20 00:00:43,260 --> 00:00:44,610 ‫very, very quickly. 21 00:00:44,610 --> 00:00:46,980 ‫Now, our load balancers, or ELB, 22 00:00:46,980 --> 00:00:48,630 ‫are allowing us to distribute traffic 23 00:00:48,630 --> 00:00:52,170 ‫across backend EC2 instances, and they can be spread out 24 00:00:52,170 --> 00:00:54,630 ‫across multiple availability zones. 25 00:00:54,630 --> 00:00:56,010 ‫We support health checks to make sure 26 00:00:56,010 --> 00:00:59,520 ‫that the backend EC2 instances are indeed healthy. 27 00:00:59,520 --> 00:01:01,350 ‫And we have four kinds of load bouncers. 28 00:01:01,350 --> 00:01:03,390 ‫The classic one is old and retired. 29 00:01:03,390 --> 00:01:06,390 ‫We have the application balancer for HTTP type of workload 30 00:01:06,390 --> 00:01:07,770 ‫at the layer seven. 31 00:01:07,770 --> 00:01:10,710 ‫Network load balancer for very high performance 32 00:01:10,710 --> 00:01:14,040 ‫and TCP level load balancing, layer four. 33 00:01:14,040 --> 00:01:17,114 ‫And finally, the gateway load balancer, layer three, 34 00:01:17,114 --> 00:01:21,480 ‫to route the network itself, and make it go by, for example, 35 00:01:21,480 --> 00:01:24,030 ‫through some virtual appliances. 36 00:01:24,030 --> 00:01:25,800 ‫We have auto scaling groups that allow us 37 00:01:25,800 --> 00:01:28,860 ‫to implement elasticity for our application, 38 00:01:28,860 --> 00:01:31,590 ‫therefore spreading our load across multiple AZ 39 00:01:31,590 --> 00:01:33,300 ‫and scaling accordingly. 40 00:01:33,300 --> 00:01:35,280 ‫So we scale these EC2 instances 41 00:01:35,280 --> 00:01:37,470 ‫based on the demand on your system, 42 00:01:37,470 --> 00:01:39,900 ‫and we can replace unhealthy instances. 43 00:01:39,900 --> 00:01:43,890 ‫There's a tight integration between the ASG and the ELB. 44 00:01:43,890 --> 00:01:46,710 ‫So this is why they are a great combination, 45 00:01:46,710 --> 00:01:50,100 ‫and together, we achieve high availability, scalability, 46 00:01:50,100 --> 00:01:52,980 ‫elasticity, and agility in the Cloud. 47 00:01:52,980 --> 00:01:53,970 ‫All right, that's it. 48 00:01:53,970 --> 00:01:57,093 ‫I hope you liked it and I will see you in the next lecture.