Ensuring Availability of Services on Azure Virtual Machines with Multiple Availability Zones

A

In an Azure Storage account that uses geo-redundant storage (GRS), the answer is A. 3.

Geo-redundant storage (GRS) is a feature provided by Azure that helps ensure high durability and availability of data stored in Azure Storage. GRS achieves this by replicating your data to multiple data centers within a selected region, as well as to a secondary region for additional redundancy.

When you enable GRS for your Azure Storage account, Azure automatically creates multiple copies of your data and maintains them across multiple data centers. Specifically, Azure creates three copies of your data:

1. Primary copies (locally redundant copies): Azure stores the first two copies of your data within the primary region where your Storage account is located. These copies are stored in different fault domains and upgrade domains to protect against hardware and software failures, as well as planned maintenance events. These copies provide local redundancy and high availability within the primary region.

2. Secondary copy (geo-redundant copy): In addition to the two primary copies, Azure creates a third copy of your data and stores it in a different region, typically located several hundred miles away from the primary region. This copy provides additional protection against a broader range of regional-level failures, such as natural disasters or prolonged outages in the primary region. The secondary copy serves as a failover option in case the primary region becomes unavailable.

By maintaining three copies of your data, GRS ensures that your data is highly durable and available even in the face of hardware failures, software failures, and regional-level disasters. If a failure occurs in the primary region, Azure automatically fails over to the secondary region, allowing you to access your data without disruption.

Therefore, the correct answer to the question is A. 3 copies of data are maintained by an Azure Storage account that uses geo-redundant storage (GRS).

An Azure Storage account that uses geo-redundant storage (GRS) provides redundancy for data in case of a regional outage. With GRS, data is stored in both the primary region and a secondary region, which is at least 400 miles away from the primary region.

The data in the primary region is replicated synchronously to three copies, whereas the data in the secondary region is replicated asynchronously to three more copies. This means that a total of six copies of data are maintained by an Azure Storage account that uses GRS, which provides high durability and availability for your data.

Therefore, the correct answer to the question is C. 6.