Skill 3.2 Configure VMs for High Availability and Scalability Flashcards
What is the recommend availability zones to create VMs in for automatic
Three when VMs are created in three Availability Zones, those will be automatically distributed across three default domains and three update domains
What are fault domains
They represent a group of servers which have shared power, cooling, and networking
What is an update domain
represents a group of servers that can be rebooted at the same time
How many virtual machines must be in an availability set to provide redundancy
2 which ensures that at least one virtual machine is available in the event of a host update
How should Availability sets be deployed
According to there workload or application tier. If you have a three-tier solution of web servers, middle tier, and a database tier then each should ahve its own availability set
How can availability sets be configured
By assigning a fault domain and an update domain. Each availability set can have up to 20 update domains and 3 fault domains. This reduces the impact to VMs from physical hardware failures
When must an availability set be set
At the creation time of the virtual machine
What is a proximity placement group
logical grouping of VMs to reduce the latency by keeping them closer to each other. If the VMs are placed in the same proximity placement group, they will be physically located closer to each other
How do availability sets and managed disks complement each other
When the vM uses a managed disk and is placed in different storage fault domains. This alignment ensures that all teh managed disks attached to a VM are within the same default domain
What is a Virtual Machine Scale Set (VMSS)
a compute resource that you can use to deploy and manage a set of identical virtual machines. By default, supports up to 100 instances but can scale up to 1000 instances by placing instances into multiple placement groups, Using multiple placement groups is referred to as a “Large Scale Set”
What is a placement group
a construct, such as an Azure Availability set, with its own fault domains and upgrade domains
What are conditions for large-scale sets “multiple placement groups”
Custom images can support up to 600 instances comapred to the normal 1000Basic SKU of the Azure Load Balancer can scale up to 300 instances
For a large-scale set (>100) you should use the standard SKU (Supports up to 1000 instances) or the Azure Application Gateway
All instances of a {{}} will use the same operating system disk image
VMSS
Three options for updating a virtual machine scale set instance
Automatic – All instances are updated in teh random order when an update is available which can cause downtime
Rolling – Updates VMs in multiple batches, and you can set a pausse time between two patches which can avoid total downtime
Manual – It is up to you to programatically step through and update each instance using the pwoershell command
What is health monitoring
For VMSS and is required when you plan to use managed infrastructure and automatic OS upgrades
