Memory-preserving maintenance works for more than 90 percent of Azure VMs. Azure increasingly uses live-migration technologies and improves memory-preserving maintenance mechanisms to reduce the pause durations. These maintenance operations that don't require a reboot are applied one fault domain at a time. They stop if they receive any warning health signals from platform monitoring tools.
These types of updates can affect some applications. When the VM is live-migrated to a different host, some sensitive workloads might show a slight performance degradation in the few minutes leading up to the VM pause.
To prepare for VM maintenance and reduce impact during Azure maintenance, try using Scheduled Events for Windows or Linux for such applications. For greater control on all maintenance activities including zero-impact and rebootless updates, you can use Maintenance Control feature.
Maintenance control gives you the option to skip all platform updates and apply the updates at your choice of time within a day rolling window. Live migration is an operation that doesn't require a reboot and that preserves memory for the VM. It causes a pause or freeze, typically lasting no more than 5 seconds.
You won't recieve a notification in the Azure portal for live migration operations that don't require a reboot. To see a list of live migrations that don't require a reboot, query for scheduled events. Some planned-maintenance scenarios use live migration, and you can use Scheduled Events to know in advance when live migration operations will start. Live migration can also be used to move VMs when Azure Machine Learning algorithms predict an impending hardware failure or when you want to optimize VM allocations.
For more information about predictive modeling that detects instances of degraded hardware, see Improving Azure VM resiliency with predictive machine learning and live migration. Live-migration notifications appear in the Azure portal in the Monitor and Service Health logs as well as in Scheduled Events if you use these services.
In the rare case where VMs need to be rebooted for planned maintenance, you'll be notified in advance. Planned maintenance has two phases: the self-service phase and a scheduled maintenance phase.
The upgrade domain concept has been introduced for Windows Azure to provide high availability services during an upgrade of an application.
The number of upgrade domains can be configured as a part of the service definition file. The default number of upgrade domains is 5, and the maximum is Windows Azure distributes instances of a role evenly when possible across a set number of upgrade domains. For example, if the default number of upgrade domains is used and a service has five instances, each instance will be assigned to an individual upgrade domain. In the case of a service having ten instances, each upgrade domain will have two instances.
In the case of a service having 14 instances, the first four upgrade domains will have three instances, and the last one will have two instances. In Azure Resource Manager ARM portal, we have three Fault domains and 5 update domains but we can upgrade our update domains from 5 to VMs are assigned sequentially in the update domains and fault domains.
Consider the below mentioned table to understand how virtual machines would be placed within Fault Domains and Update Domains inside an availability set. You need to create virtual machines in the same resource group as the availability set. One virtual machine can only be in one availability set. You can assign virtual machines to the availability set only during the creation of virtual machines. You should create separate storage accounts for each virtual machine.
Next Recommended Reading. Fault domains define the group of virtual machines that share a common power source and network switch. By default, the virtual machines configured within your availability set are separated across up to three fault domains for Resource Manager deployments two fault domains for Classic. While placing your virtual machines into an availability set does not protect your application from operating system or application-specific failures, it does limit the impact of potential physical hardware failures, network outages, or power interruptions.
For more details, refer this documentation. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Asked 4 years ago. Active 4 years ago.
Viewed 2k times.
0コメント