AZ-900:Describe cloud concepts ④


AZ-900の試験を英語で受けるに至り、翻訳なしで勉強をしてまとめていく勉強ノートです。

自身の復習用としても記事を書くつもりではありますが、同じように英語で受講予定＆翻訳なしでそのまま英語で勉強した方がやりやすい方の参考に少しでもなることが出来ればと思います。

日本語で勉強をしたい方は、こちらのサイトを是非参考にしてみてください：

https://qiita.com/fsd-jume/items/3ff16444827addf2cfa2

# 学習内容
Describe the benefits of using cloud services
Describe the benefits of high availability and scalability in the cloud

- [学習内容](#学習内容)
- [High availability](#high-availability)
- [Scalability](#scalability)
- [Vertical scaling](#vertical-scaling)
- [Horizontal scaling](#horizontal-scaling)

<a id="#high-availability"></a>
# High availability

Availability of resources when need is important.
 →High availability focuses on ensuring maximum availability.

Azure is a highly available cloud environment with uptime guarantees.
The guarantees are part of service-level-agreements (SLAs).

What is SLAs?
* Formal agreement between service providers and customer that guarantees the customer a stated level of service.

What SLAs mean for Azure
* Up time - Represented as percentage
  * Related to the service or application availability aka up time
    * If the service was always available to use == 100% up time
* Down time
  * When the service is unavailable
* Credit
  * Credit a customer may be entitled to if the SLA is not met.
* Each Azure service has its own SLA

Azure services’ uptime: mostly 99%~99.9%

99% == can be unavailable for up to…
* 1.6 hours / week
* 7.2 hours / month

99.9% == can be unavailable for up to…
* 10 min / week
* 43.2 minutes / month

<a id="#scalability"></a>
# Scalability

*  Ability to adjust resources to meet demand.
* able to add more resources to better handle the increased demand, when systems are overwhelmed from a sudden peak traffic.
* No overpayment for services
	* As the cloud is a consumption-based model == pay only for what is used.
	* can reduced resources and costs if demand drops off

Comes in two varieties: vertical and horizontal.

**Vertical-scaling**
Focused on increasing or decreasing the capabilities of resources.

**Horizontal-scaling**
Adding or subtracting the number of resources


<a id="#vertical-scaling"></a>
# Vertical scaling

**Vertical scale up**
When more processing power is needed while developing an app
* adds more CPUs or RAM to the virtual machine

**Vertical scale down**
When you realized you had over-specified the needs
* lowers CPU or RAM specifications.

<a id="#horizontal-scaling"></a>
# Horizontal scaling

**Scaling out** deployed resources (either automatically or manually)
If there is a sudden steep jump in demand.

Scaling out ex:
* add additional virtual machines or containers

**Scaling in** deployed resources (either automatically or manually)
If there is a significant drop in demand.

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AZ-900:Describe cloud concepts① はこちら：

https://qiita.com/fsd-lukapyon/items/0100596156d3abc7808e

AZ-900:Describe cloud concepts② はこちら：

https://qiita.com/fsd-lukapyon/items/99edd38b566f6ed0d096

AZ-900:Describe cloud concepts③ はこちら：

https://qiita.com/fsd-lukapyon/items/0324140f0b6c2034db68

AZ-900:Describe cloud concepts⑤ はこちら：

https://qiita.com/fsd-lukapyon/items/3d489123078f765ccb87

AZ-900:Describe cloud concepts⑥ はこちら：

https://qiita.com/fsd-lukapyon/items/6b5e612044dd37b42386

AZ-900:Describe cloud concepts⑦ はこちら：

https://qiita.com/fsd-lukapyon/items/83390ae397ff8e7b8989

AZ-900:Describe cloud concepts⑧ はこちら：

https://qiita.com/fsd-lukapyon/items/abfc398d55bf28160b90

AZ-900:Describe cloud concepts⑨ はこちら：

https://qiita.com/fsd-lukapyon/items/4881ce9db481dd4173eb