Virtual Machines Flashcards
What is the purpose of an account in Azure?
Accounts serve the following purposes:
- Uniquely identifying users
- Applying security policies to users
- Associating resource subscriptions with users
What is the purpose of subscriptions in Azure?
Subscriptions are what grant users access to resources in Azure,
Can an account have multiple subscriptions?
Yes, accounts can have multiple subscriptions of varying types.
What are four different types of subscription models?
Common subscriptions types include:
- Free account subscriptions
- Pay-as-you-go subscriptions
- Visual Studio subscriptions
- Enterprise agreements
What is the purpose of the Resource Manager?
The main functions of the Resource Manager are:
- Creating resource groups
- Managing resources associated with resource groups, such as creating template deployments
- Managing resource billing at a resource group level
- Providing consistent tooling between the Azure CLI, SDK and PowerShell tooling
What is the technical definition of a region?
Regions are sets of collocated data centres within a certain geographical perimeter that are interconnected by low-latency networks.
What is the primary benefit of using a region-based model?
End users can specify to have resources deployed in certain regions based on client requirements, regulatory restrictions or latency considerations.
What is the technical definition of an availability zone?
Availability zones within a region are geographically-isolated data centres that operate independently and are connected via a dedicated, low-latency interconnect network
What are three primary benefits of having multiple availability zones in a region?
The three primary benefits of having multiple availability zones are:
- Redundancy: If one data centre suffers data loss or an outage, other availability zones have redundant copies of the data
- Availabilty: If any given data centre experiences an outage, other availability zones can keep the public services running
- Latency: By connecting to geographically-close availability zones, data access has much lower latency, which is ideal for critical applications
What are four major considerations when deciding which regions and availability zones will be used for deploying resources?
Four major considerations are:
- Whether the resource is available in that region and AZ, as new resource types are released to regions on a rolling basis
- Geographical location of the region and AZ and any regulatory restrictions concerning the housing of data in those areas
- Whether multiple AZs within that region are available for mission-critical services that require redundancy
- The proximity of the AZs to the end users of services, ideally optimising for keeping the producers and consumers of data as close as possible
What are the two major service models offered in Azure?
The two major models are:
- Infrastructure as a Service (IaaS)
- Platform as a Service (Paas)
What is the definition of an Infrastructure as a Service (IaaS) model?
An IaaS model provides the end user full control of the virtual machine instances, storage, database access and all other required infrastructure to serve the end user’s business needs. Maintenance of the physical infrastructure is managed by the cloud provider.
What is the definition of a Platform as a Service (PaaS) model?
A PaaS model provides resources that are directly usable in end user applications, such as access to databases, storage, web services and other components of an application. The underlying infrastructure concerns, patching, availability and maintenance are handled by the cloud provider.
What are four benefits of using virtual machines in an IaaS model that could not be accomplished as easily in a PaaS model?
The main benefits of an IaaS model with explicit virtual machines include:
- Patching: Users can install patches as soon as they are released, instead of relying upon the cloud provider to roll out patches
- Version control: Specific version dependencies for certain applications, operating systems and patch versions can be controlled by end users
- Instrumentation: Utilities can be installed to provide detailed telemetry, logging and automation that are not available in PaaS offerings
- Security and compliance: Regulations around data storage, security, access controls and other requirements can be accommodated in a flexible IaaS model
What functions do virtual machine images serve?
The primary functions of virtual machine images include:
- Containing pre-built configurations of virtual machine instances that specify the operating system and pre-configured software available when the virtual machine is initialised
- Deploying standard application infrastructure components such as Citrix VPNs
- Providing users the ability to specify their own custom virtual machine image configuration templates to rapidly deploy new virtual machines
What are the three principal components of a VM?
The principal components of a VM are:
- The virtual machine image
- The attached virtual network adapter
- The attached block storage devices
What is the function of the network adapter attached to a virtual machine?
A virtual machine’s network adapter allows the virtual machine to have both a public and private IP address in order to communicate with other internal Azure resources and external resources via the Internet.
By default, how is storage allocated to a VM for storing operating system files?
If no block storage volumes are explicitly configured for a VM, a default block storage volume is created that is used as the boot volume, which has the operating system files installed on it.
What are two steps that should be performed in preparation for creating a virtual machine?
Before creating a virtual machine, it is best to:
- Create a resource group if one does not already exist to logically organise the VM and any other resources created along with it
- Create a virtual network and subnet to specify the constraints for the public and private IP address created for that VM
What are eight examples of settings that can be specified when creating a VM?
- The image used to initialise the boot volume for that virtual machine
- Whether the attached block storage volume is SSD or HDD based, and which volumes should be created
- The username and password (or a username and public SSH key for Linux VMs) used when connecting to the VM
- Which subscription the virtual machine will be associated with
- The resource group in which the virtual machine will reside,
- The network configuration, including which public IP address should be used for the virtual machine
- The security group configuration, including which ports should be publicly exposed
- The size of the virtual machine, measured in terms of number CPUs and amount of RAM
What is the main difference between the authentication modes available for Linux and Windows VMs?
Windows VMs are always accessed via a username and password, while Linux VMs support both username and password and public SSH key authentication.
