Azure Storage Redundancy is a critical concept for every Azure Administrator to master, especially for those preparing for the AZ-104 Microsoft Azure Administrator Exam. This feature guarantees the availability and durability of your data stored in Azure.
Understanding Azure Storage Redundancy
Azure Storage redundancy minimizes the impact of potential data loss scenarios, like hardware failures, by creating and maintaining replicas of your data. Depending on the option you choose, Azure can keep these replicas within a single data center, across zonal data centers within the same region, across geographically separate regions, or even across two regions with the data being read-accessible in the second region.
There are four redundancy options in Azure:
- Locally Redundant Storage (LRS)
- Zone-Redundant Storage (ZRS)
- Geo-Redundant Storage (GRS)
- Read-Access Geo-Redundant Storage (RA-GRS)
1. Locally Redundant Storage (LRS)
With LRS, Azure keeps three replicas of your data in a single data center within a region. These replicas are always in sync, and Azure automatically handles any issues that arise in keeping them updated. It’s the most cost-effective option, but it doesn’t protect against regional disasters.
2. Zone-Redundant Storage (ZRS)
ZRS options offer durability by replicating data across three Availability Zones within the same region. Each Availability Zone is a unique physical location with its own power, cooling, and networking, offering better protection against local hardware failures.
3. Geo-Redundant Storage (GRS)
This option is an extension of LRS. Azure replicates your data to a secondary region, hundreds of miles away from the primary region, offering resilience against regional disasters. The data in the secondary region, however, is not accessible for read or write operations.
4. Read-Access Geo-Redundant Storage (RA-GRS)
RA-GRS adds read-accessibility to the replicated data in the secondary region. In the event of an outage in the primary region, you can read your data from the secondary region.
Implementing Azure Storage Redundancy.
In selecting your Azure Storage account, you must choose a redundancy option. Here’s how to do it:
Go to the Azure portal:
- In the left menu, click on “Storage accounts.”
- Click on “Add” to create a new storage account.
- In the new storage account blade, choose your subscription and resource group.
- Enter a name for your new storage account.
- Select a location for your storage account.
- In the redundancy drop-down menu, select your preferred redundancy option (LRS, ZRS, GRS, RA-GRS).
- Click on “Review + create” to create the storage account with the selected redundancy.
Take note that once you’ve created a storage account, you cannot change its redundancy type except for upgrading from GRS to RA-GRS. Therefore, you must choose carefully during the creation phase, considering your data availability and durability requirements along with the cost implications.
You’re now ready to implement Azure Storage redundancy, an important aspect for Azure administrators on the path to AZ-104 certification!
Practice Test
True or False: Azure Storage service offers four types of redundancy for protecting your data: local redundancy, zone-redundant storage, geo-redundant storage, and read-access geo-redundant storage.
- True
- False
Answer: True
Explanation: Azure does indeed provide four redundancy options to protect data: Locally redundant storage (LRS), Zone-redundant storage (ZRS), Geo-redundant storage (GRS), and Read-access geo-redundant storage (RA-GRS).
Azure Storage redundancy can only be set when the account is first created, and cannot be modified later. True or False?
- True
- False
Answer: False
Explanation: You can, in fact, alter the redundancy level after the fact. However, the transition from a lower to a higher level of redundancy may incur additional costs.
Select the correct statement about Geo-Redundant Storage (GRS)?
- A. GRS replicates your data to an additional geographic location that is hundreds of miles away from the primary location.
- B. GRS only replicates your data within the same geographical location.
Answer: A. GRS replicates data to an additional geographic location that is hundreds of miles away from the primary location.
Explanation: GRS is designed to provide maximum durability and availability for your data, even in the face of a major regional disaster.
Which Azure Storage redundancy option allows read access to the secondary data center?
- A. Locally redundant storage (LRS)
- B. Zone-redundant storage (ZRS)
- C. Geo-redundant storage (GRS)
- D. Read-access geo-redundant storage (RA-GRS)
Answer: D. Read-access geo-redundant storage (RA-GRS)
Explanation: RA-GRS provides read-only access to the data in the secondary location, in addition to replicating the data there.
True or False: ZRS or Zone-redundant storage replicates data across three different storage zones in one region.
- True
- False
Answer: True
Explanation: ZRS copies data synchronously across three Azure availability zones in the same region to protect from local failures.
What happens when data written to a storage account with LRS redundancy fails?
- A. Data is automatically replicated to another region.
- B. Data is automatically replicated within the same region.
- C. Data is lost.
- D. None of the above.
Answer: B. Data is automatically replicated within the same region.
Explanation: When LRS redundancy fails, the data is automatically replicated three times within the same physical location in the data center.
Data in an RA-GRS storage account should be used for?
- A. Backup or archival purposes.
- B. Structured data.
- C. Operations that require read access in a secondary region.
- D. Large scale data.
Answer: C. Operations that require read access in a secondary region.
Explanation: RA-GRS storage accounts provide read-only access in a secondary region to ensure high availability.
True or False: Azure Storage redundancy is set at the resource group level.
- True
- False
Answer: False
Explanation: Azure Storage redundancy is set at the storage account level, not at the resource group level.
Which Storage redundancy option has the highest write latency in Azure Storage?
- A. Locally redundant storage (LRS)
- B. Zone-redundant storage (ZRS)
- C. Geo-redundant storage (GRS)
- D. Read-access geo-redundant storage (RA-GRS)
Answer: C. Geo-redundant storage (GRS)
Explanation: GRS has the highest write latency as the data needs to get replicated to a secondary region that is far from the primary region.
With regards to Azure Storage redundancy, what does Azure promises in terms of data durability over a given year?
- A. At least 9% durability
- B. At least 99% durability
- C. At least 999999999% durability
- D. At least 9999999999% durability
Answer: C. At least 999999999% durability
Explanation: Depending on the option you choose, Azure Storage offers a high level of data durability, in the range of 11 nines (999999999%).
Interview Questions
What is Azure Storage redundancy?
Azure Storage redundancy is a feature that ensures that your data is safe in the event of a transient hardware failure, network or power outage. It provides multiple copies of your data by automatically replicating it to different locations in the Azure network.
What are the types of storage redundancy in Azure?
Azure offers four types of storage redundancy: Locally redundant storage (LRS), Zone-redundant storage (ZRS), Geo-redundant storage (GRS), and Read-access geo-redundant storage (RA-GRS).
What is Locally Redundant Storage (LRS)?
LRS is a redundancy option that replicates your data three times within a single storage scale unit in a single region. It protects your data from hardware failure but not from the failure of the entire region.
What is Zone-Redundant Storage (ZRS)?
ZRS replicates your data synchronously across three Azure availability zones in the same region. It helps to protect your data from zone-level failures.
What is Geo-Redundant Storage (GRS)?
GRS replicates your data to a secondary region far away from the primary region. It is designed to provide at least 99.999999999% (11 9’s) durability of objects over a given year.
What is Read-Access Geo-Redundant Storage (RA-GRS)?
RA-GRS allows you to have read access to your data in the secondary region, in addition to geo-replication across two regions provided by GRS.
Can the type of data redundancy be switched after the storage account has been created?
Yes, data redundancy can be changed after storage account creation. You can switch from LRS to GRS, ZRS or RA-GRS and vice versa.
How is ZRS different from GRS?
ZRS replicates data across multiple availability zones in the same region, providing resilience in the event of zone-level failures. On the other hand, GRS replicates data to a second region that is geographically distant from the original region, providing resilience in the event of a major disaster.
Can I access my data during an Azure initiated failover in GRS?
No. Your storage account is unavailable during an Azure initiated failover in GRS. Azure provides access to the data from the secondary region only after completing the failover process.
Is there any requirement to enable Geo-Redundant Storage (GRS)?
No, there are no requirements necessary for enabling GRS. However, you need to understand that GRS may cost more than LRS and ZRS due to the additional data replication to the second region.
What happens if I delete my data from the primary region when using GRS?
When you delete data from the primary region, the system will also delete the data from the secondary region. Deleting data in the primary region is immediately and automatically mirrored in the secondary region.
Can I choose the secondary region for my GRS data?
No, Azure manages the secondary region for your GRS data. The secondary region is chosen based on the mapping specified by Microsoft Azure.
Are there any benefits of using Read-Access Geo-Redundant Storage (RA-GRS)?
Yes, RA-GRS offers several benefits such as allowing clients to read data from the secondary location, offering higher read availability, and providing additional latency benefits for clients that are closer to the secondary location.
Can I force my data to failover to the secondary location with RA-GRS?
Yes, in the event of a disaster that renders the primary location unavailable, you can force a manual failover to use the secondary location with RA-GRS.
Is the pricing of Azure Storage affected by the type of redundancy chosen?
Yes, the type of redundancy chosen affects the cost. Geo-replication options such as GRS and RA-GRS are more expensive than LRS and ZRS due to the additional replication and storage resources used in multiple regions.
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