Azure Questions & Answers - 2

1. What is Azure Cloud Service & the usefulness of it?

Cloud service is a term that means more than one thing, but in summary it's a logical group.

There's also Worker and Web Roles that usually are referred as Cloud Service too. So, what is Cloud Service, depends on context.

Cloud Services are ways to combine a set of stateful virtual machines (or web/worker role instances, which are stateless virtual machines) into its own private network, sitting behind a public virtual IP address. Cloud service is a management and security boundary for VMs

Cloud Service also provides optional load-balancing between the virtual machines

Originally, the cloud service was a network isolation container into which compute resources are placed. It is used for Azure PaaS and IaaSv1 resources. Its considered "legacy" and is not present in Azure's IaaSv2 which is based on the new Azure Resource Manager model

v1 is the version of IaaS that was launched in 2012. IaaS v2 uses Azure Resource Manager (ARM) API's

2. What are the different ways in which Traffic Manager decides to which endpoint to route traffic?

• Round-Robin
• Failover
• Performance

3. What is the maximum bandwidth provided by ExpressRoute?

1 Gbps when a Network Service Provider is used and 10 Gbps with an Exchange Service Provider

4. How many data drives can you attach to a Standard_G5 VM (the biggest size in the series)?

64 data drives which can provide the maximum IOPS of  32000 (64 X 500)

5. While considering lifting and shipping existing applications to Azure VMs, what are the challenges to prepare for?

Reliability, availability, security, and performance are all important concerns.

Especially, because Azure provides SLAs only if there are at least two VMs in an Availability Set, to ensure availability, you’ll need to deploy the application to at least two VMs and join them behind a load balancer. This might immediately cause some problems because not all applications are designed for such deployment. For instance, some of the legacy systems are designed to have a single central server that handles all user transactions. When the transactions are distributed to multiple instances, you might have two centers of truth that can’t be reconciled. Data replication and customer partition are two effective approaches in some cases.


6. When you have servers running on both on-premises and the cloud, it’s almost unavoidable that you will experience some performance degradation because of the extra network latency. What code changes would you make to reduce latency?

Common techniques include introducing cache to reduce accesses to databases, using asynchronous IO operations, compressing data, sending deltas and only required data instead of complete data sets, and paging.

7. What is the difference between Upgrade Domain and Fault Domain?

Upgrade domains are similar to Fault domains in function, but they support upgrades rather than failures.

An Upgrade domain is a logical unit of instance separation that determines which instances in a particular service will be upgraded at a point of time

A Fault domain boundary is basically a different hardware rack in the same datacenter. Fault domains don't share a common power source or network switch

8. What is the difference between Access Control Lists & Network Security Groups?

You can use both network Access Control Lists (ACLs) and Network Security Groups (NSGs) to control traffic to your VMs. In either case, the traffic is filtered before it reaches your VM so that your machine doesn’t need to spend extra cycles on packet filtering.

NSGs are different from ACLs in a couple of aspects:
* ACLs are applied to traffic with a specific VM endpoint, whereas NSGs are applied to all traffic
that is inbound and outbound on the VM.
* ACLs are associated to a VM endpoint, whereas NSGs are associated to a VM, or a subnet
within a virtual network.

9. What are the different sources of images for a Azure VM?

• Azure VM Gallery
• VM Depot
• Custom images

10. What is the role of Internal Load Balancers?

ILBs provide load balancing among VMs residing in a Cloud Service or a regional virtual network. ILBs (Internal Load Balancers) are not publicly accessible.

Note - Features of Azure services may change at any time.

Reference - Exam Ref 70-534 Architecting Microsoft Azure Solutions

Azure Questions & Answers - 1

1. Name the "kernel" of the Azure Cloud operating system

Fabric Controller (FC). It provisions, stores, delivers, monitors and commands the virtual machines (VMs) and physical servers that make up Azure.

2. Critical business applications require a low RTO & RPO. True or False

True

3. Scaling-out is a preferable scaling method for cloud applications than scaling-up - True or False

True. Scaling up is constrained by what VM sizes are available

4. Azure organizes VM sizes into different machine series. What are they & what is specialty of each series?

• A series - generic workloads
• A8-A11 - high performance computing
• D series - high CPU & high temporary data IO
• DS series - high I/O workloads
• G series - high CPU & high memory demands

5. When you create a VM in Windows Azure you are provided with a temporary storage automatically. What is the location of this storage

This temporary storage is “D:” on a Windows VM and it is “/dev/sdb1” on a Linux VM.

6. What is the purpose of temporary storage in VMs?

This temporary storage is used to save the system paging file.

You can also use this drive only to store temporary data, which you can afford to lose at any time.

Like for example: If your workflow involves getting content from the blob, processing it and storing it back to the blob then you could download content to the temporary storage, process the content, then take the processed content and save it back to the blob.

7. When will the data on temporary drive in a VM be lost?

When you resize the VM, when you shutdown or restart your VM, when your VM is moved to a different host server(due to service healing, shutdown and restart), when the host is updated, when the host experiences a hardware failure etc.

8. Is there any cost associated with temporary storage?

The temporary storage provided with each VM has no extra cost associated with it for storage space as well as for transactions.

9. How are VHDs in Azure Storage charged?

VHD's are persisted as page blobs and so you are charged for the space consumed in the blob. 

For Windows Azure Drive storage, you will be billed only for the storage space used by the page blob and the read/write transactions to the page blob. You will not be charged for read transactions that utilize the local drive cache. Windows Azure Drive usage is billed at the same rates as standard Windows Azure Storage and is included with Windows Azure Storage usage in your bill. - Official Azure documentation

10. If I place VMs in different cloud services in Azure, can they still talk to each other?

Yes. All VMs within the cloud service can communicate with each other via the DIP. VMs in different cloud services can communicate via endpoints defined on the cloud service VIP. Although this is fine for limited communications, it isn't efficient.

The better solution is to place the cloud services in a virtual network, which then allows all the VMs in cloud services on the same virtual network to communicate directly using the internal (DIP) addresses

Note - Features of Azure services may change at any time.