cloud computing note(1)
1.Cloud computing is a technology that you need it, you get it.
Amazon provides instantaneous self-service access to servers called EC2, which is VMs running on the cloud.
AWS -> Amazon Web Service
AWS EC2-> AWS Elastic Computing Cloud
Cloud computing could save our time to configure servers or other things and save money to buy hardware. This makes IT become a resource other than a tool.
The spending of cloud computing increases in these years and becomes the number 2 of spending increases. And security is number 1. At the same time, hardware spending is currently decreasing.
We can rent IT stuff from providers and this is measured service.
2.SaaS: Software as a service. If you want to have a software, you can have it. We can connect to the web page, then we have this software and don’t need to think about how to code or install. For example, office365 web application.
Software Plus Service: a software will provide a interface to link with other software by using API, this software can improve some features, like PayPal.
When we use SaaS, our data will not be saved locally. SaaS venders are Google Apps, Microsoft Office 365 and Salesforce.com.
Google provides a lot of applications, such as Word processing, Spreadsheet, Presentation, Calendar, Photo sharing, Website creation and so on.
3.PaaS: Platform as a service. Using this, we just need to know how to code or run the code but don’t need to know about configuration of the system and environment. we don’t have to configure the middleware, we need to push the code to run, like wordPress.
Platform is sum of hardware and software components. It can host your application and make your application available to people. Different applications will require different platforms.
Middleware is the layer between operating system and application, like MySQL, PHP and Apache.
3 stages for the coding in same platform:
- Staging: Staging is before you can make your code be available to the people, and you can modifying and testing your code.
- Production: you could make your code be available to the people.
Platforms fall into two categories:
–For developers/programmers who write code.
–For nonprogrammers to develop business applications: non programmer people want to public some applications, like wordPress give direct access to wordPress that you can host your content.
Microsoft Azure PaaS: cloud service for Microsoft.
Microsoft Azure Websites provide a managed web environment. It will be managed as VM and also can be added or removed by the space of usage, which means it can load balance automatically.
It has two modes of execution:
–Shared mode: you will share the same vm with others.
–Reserved mode: your VM only have your code.
Web role instance accepts HTTP and HTTPS requests, Worker role deals with requests and response it.
4.IaaS: Infrastructure as a service. IT resources are delivered as a service, including networks, servers, storage, and so on. For example, AWS(Amazon Web Services), GCE(Google Compute Engine) and Microsoft Azure IaaS.
When we use Amazon Compute Service, we pay the IO of the disk, storage, CPU and RAM. The connection from VM to VM is free. We need to pay the connection from VM to internet.
AMI: Amazon Machine Image, a template for the server which contains the core operating system, plus pre-installed tools and software.
Instance: the running virtual server created from AMI template.
EBS: Elastic block storage,block level storage volume mountable from an EC2 instance.
Snapshot: we can keep a snapshot as a AMI template.
A AMI could create 0 to many instances. A security group has many VMs to tell the VM which door is opened from the internet.