Design Azure Compute

Question 1

Machine series

Answer 1

1) A-series VMs are designed for generic workloads
2) D-series VMs use solid-state drives (SSDs) for temporary storage, providing much faster IO operations
3) DS-Series VMs are designed for high I/O workloads. They use SSDs for both VM drives and a local drive cache
4) G series of VMs is one of the biggest on cloud with Xeon E5 V3 family processors

Question 2

Temporary Disks

Answer 2

Both OS drives and data drives are virtual hard drives (VHDs) stored in Azure Blob Storage. Their data is automatically duplicated three times for reliability. However, the temporary drives reside on the hosting servers. If the host fails, your VM will be moved to a healthy host, but not the temporary drive. In this case, you’ll lose all temporary data.

Question 3

Managing images

Answer 3

the Azure VM gallery, VM Depot, and custom images. You can use these images as foundations to create, deploy, and replicate your application run-time environments consistently for different purposes such as testing, staging, and production.

Question 4

Capturing custom images

Answer 4

1) two types of images: generalized or specialized.
2) A generalized image doesn’t contain computer or user-specific settings. These images are ideal for use as standard templates to rollout preconfigured VMs to different customers or users. Before you can capture a generalized image, you need to run the System Preparation (Sysprep) tool in Windows, or use the waagent –deprovision command in Linux.

Question 5

Capturing generalized images

Answer 5

Before you can capture a generalized image, you need to shut down the VM. After the VM is captured as an image, the original VM is automatically deleted.

Question 6

Specialized images

Answer 6

Specialized images, conversely, retain all user settings. You can think of specialized images as snapshots of your VMs. These images are ideal for creating checkpoints of an environment so that it can be restored to a previously known good state. You don’t need to shut down a VM before you capture specialized images. Also, the original VM is unaffected after the images are captured.

Question 7

Problems with Custom images

Answer 7

1) difficult to revise a custom image
2) difficult to track what has been changed on an image because of the manual customizations.
3) To deploy a new image version, the VM needs to be re-created, making upgrade a lengthy and complex proces

Question 8

VM extension

Answer 8

1) a light-weight Azure Virtual Machine Agent (VM Agent) is installed on the VM by default.
2) to dynamically customize VMs to satisfy your application, configuration, and compliance needs

Question 9

Custom Script Extension and DSC

Answer 9

Custom Script Extension downloads and runs scripts you’ve prepared on an Azure Blob storage container. You can upload Azure PowerShell scripts or Linux Shell scripts, along with any required files, to a storage container, and then instruct Custom Script Extension to download and run the scripts.

Question 10

Azure Automation

Answer 10

monitor events in VMs as well as external services such as Azure App Service Web Apps, Azure Storage, and Azure SQL Server. Then, workflows can be triggered in response to these events.

Question 11

Chef and Puppet

Answer 11

Both Chef and Puppet install agents on your VMs. These agents monitor your VM states and periodically check with a central server to download and apply updated cookbooks.

Question 12

Runbook gallery

Answer 12

Automation’s cookbooks, called runbooks, are implemented as Azure PowerShell Workflows. To help you to author these runbooks, Azure has created an Azure Automation Runbook Gallery where you can download and share reusable runbooks

Question 13

Infrastructure code

Answer 13

“infrastructure” indicates that it’s not business logics but instructions to configure the application runtime. Second “code” indicates that it’s not subject to human interpretation but can be consistently applied by an automation system.

Question 14

Devops and infrastructure code

Answer 14

1) Infrastructure code is explicit and traceable, and it makes an application consistently deployable.
2) Consistently deployable applications are one of the key enabling technologies in the DevOps movement.

Question 15

Azure Resource Template

Answer 15

1) JSON files that capture infrastructure as code. You can capture all the Azure resources your application needs in a single JSON document that you can consistently deploy to different environments.
2) All resources defined in an Azure Resource Template are provisioned within a Resource Group, which is a logical group for managing related Azure resources.

Question 16

Containerization

Answer 16

1) consistently deploy applications by packaging them and all their required resources together as a self-contained unit.
2) check them in to a repository, manage their versions, and reconcile their differences just as how you would manage source code.

Question 17

Containers agility

Answer 17

1) containers are much more light weight because containers use process isolation and file system virtualization
2) Containers running on the same VM share the same system core so that the system core is not packaged as part of the container.
3) Because starting a new container instance is essentially the same as starting a new process, you can start containers quickly—usually in time frames less than a second

Question 18

Containers Compute Density

Answer 18

1) achieve much higher compute density in comparison to using VMs
2) can provide cheaper and more agile compute services to your customers

Question 19

Decouple Compute and Resource

Answer 19

1) workloads running in them are not bound to specific physical servers or VMs.
2) With containers, servers are no longer assigned with specific roles. Instead, they form a cluster of CPUs, memory, and disks within which workloads can roam almost freely.

Question 20

Container orchestration

Answer 20

1) Docker Swarm, CoreOS Fleet, Deis, and Mesospher
2) foundation of container-based PaaS offerings by providing services such as coordinated deployments, load balancing, and automated failover.

Question 21

Container orchestration properties

Answer 21

1) ideal hosting environment for applications that use Microservices architecture.
2) can join multiple containers together to form a replica set for the service

Question 22

Automate container

Answer 22

can automate container cluster provisioning by using a combination of Azure Resource Template, VM Extensions, Custom Script Extension, and scripts. The template describes the cluster topology, and VM extensions perform on-machine configurations. Finally, automated scripts in containers themselves can perform container-based configurations.

Question 23

Scaling applications on VMs

Answer 23

1) Scale up

2) Scale out

Question 24

Scaling-up

Answer 24

1) increasing the compute power of the hosting nodes.
2) increase the capacity of the servers by increasing memory, processing power, or drive spaces.
3) constrained by the number of hardware upgrades you can fit into the physical machines.
4) In the cloud, choose a bigger VM size.
5) constrained by what VM sizes are available.

Question 25

scaling-out

Answer 25

1) brings in more hosting nodes to share the workload.
2) no theoretical limit
3) possible for an application to be scaled to very high capacity
3) preferable scaling method for cloud applications.

Question 26

Internal Load Balancers (ILB)

Answer 26

1) for multitiered applications
2) to scale-out middle tiers that aren’t directly accessible from the Internet.
3) have a website as the presentation layer, and a number of VMs as the business layer.
4) don’t want to expose the business layer, and thus you made it accessible only by the presentation layer

Question 27

Internal Load Balancers (ILB) properties

Answer 27

1) not publically accessible
2) can access them only by other roles in the same Cloud Services, or other VMs within the same virtual network.
3) ILB provides an ideal solution for scaling a protected middle tier without exposing the layer to the public.

Question 28

Autoscale

Answer 28

1) VMs manually in a Cloud Service.
2) Can also set up autoscale rules to dynamically adjust the system capacity in response to average CPU usage or number of messages in a queue.
3) you need to add the VMs to an Availability Set.

Question 29

Autoscale policy items

Answer 29

1) Edit Scale Settings For Schedule
2) Scale By Metric
3) Instance Range
4) Target CPU
5) Scale Up By
6) Scale Down By

Question 30

Autoscaling after the First Hour

Answer 30

Because autoscaling uses the average value of the past hour, it’s not triggered as frequently as you might have expected.