This is a continuation of an article that describes operational considerations for hosting solutions on Azure public cloud.

Multiple-choice questions in certification examinations are quite costly to make a mistake because they go beyond the cursory knowledge on the Azure resources. We recap just a few of the storage related questions from a recent test.

1.       The storage-based questions are somewhat easier to answer because they apply to a lot of common use cases. Some attention to limits imposed on different types of storage, their access polices, tiers, and retention period will go a long way in getting the answers right. Familiarity with hot, cool and archive tiers are tested by their use cases. Access control policy enforcement and cost management apply just as much they do for all Azure resources. Redundancy and availability are special considerations. Geo-replication is a hot topic.

2.       Hot, cool and archive access tiers for blob data are optimized for access patterns. The hot tier has the highest storage cost but the lowest access cost.  The cool tier stores for a minimum of 30 days and the archive tier for a minimum of 180 days. The archive tier is an offline tier for storing data with data rehydration available on standard and priority basis. The storage capacity costs Hot tier can be set to cool tier or archive tier and cool tier can be set to archive tier. If a blob is moved from the archive tier to the hot tier, it will be moved back to the archive tier by the lifecycle management engine. End-to-End latency and server latency are both available for block blobs.

3.       Azure storage events allow application to react to events such as the creation and deletion of blobs. They are pushed using Azure Event Grid to subscribers such as Azure Functions, Azure Logic Applications or even to the http listener. Blob storage events schema defines Microsoft.Storage.BlobCreated, BlobDeleted, BlobTierChanged and AsyncOperationInitiated.

4.       Network File System (NFS) 3.0 protocol is supported in Azure Blob Storage. Mounting a storage account container involves creating an Azure Virtual Network (VNet) and configuring network security to allow traffic to and from the storage account container via the VNet. Azurite open-source emulator can be used for local development environment.

5.       Azure (global) supports General Purpose V1, V2, and Blob storage accounts while Azure Stack Hub is general-purpose v1 only.  V2 is preferred because it provides Blob, queue, file and table storage with LRS, GRS, RA-GRS redundancy options

6.       Costs for storage tier is based on amount of data stored depending on the access tier, the data access cost, the transaction cost, the geo-replication data transfer cost, the outbound data transfer cost, and the changing storage access tier. The primary access pattern for the blob storage in terms of reads and writes and their comparisons determines the cost savings. All storage accesses can be monitored, and metrics emitted include capacity costs, transaction costs, and data transfer costs.