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Confused by AWS Storage Gateway? Here's a 'Made Easy' Explanation

I am an AWS Certified Solutions Architect currently preparing for the AWS Certified SysOps Administrator – Associate exam

When I was preparing for the AWS Certified Solutions Architect – Associate exam, it took me a while to wrap my head around Storage Gateway and the four flavors it comes in. For the test, you'll be given a scenario and then asked to choose which one of these four types to use. Questions on Storage Gateway are very likely to come up in the exam, but even a basic understanding should be enough to help you ace these questions. The important thing is being able to tell them apart. I'm going to make this very simple to understand by comparing each option to something you already know.

This is the official AWS description of Storage Gateway:

"AWS Storage Gateway is a hybrid cloud storage service that gives you on-premises access to virtually unlimited cloud storage."

Official descriptions like this can be confusing at first. But let's break it down.

  • It's a storage service
  • It's for hybrid storage (hybrid meaning both on-premises and cloud)
  • It's for use on-premises
  • It gives you virtually unlimited cloud storage

There are 3 types of storage in Storage Gateway:

  • File Gateway
  • Tape Gateway
  • Volume Gateway

For the exam though, you need to know the difference between 4 options and learn 5 different terms because Volume Gateway offers two different services.

  • File Gateway
  • Tape Gateway
  • Volume Gateway
    • Cached Volumes
    • Stored Volumes

All this terminology is what makes learning Storage Gateway so confusing.

File Gateway

The easiest way to understand the definition of a File Server is to think of a mailbox on a street corner. Any individual or business can drop their mail into that single mailbox. It will be filled with letters and packages from lots of different people.

A File Server is like that mailbox. It's a central computer that lots of other computers (the people mailing letters) can connect to. File Servers are useful for collaboration. Let's imagine a File Server called MyFileServer. Bob using Laptop A saves a document called BusinessPlan.docx to MyFileServer. Later, Jane using Laptop B accesses BusinessPlan.docx and make changes to it. Priyanka using Laptop C checks BusinessPlan.docx the next day to make sure it's accurate.

Here is the AWS description of File Gateway:

"A file gateway simplifies file storage in Amazon S3, integrates to existing applications through industry-standard file system protocols, and provides a cost-effective alternative to on-premises storage."

Think of File Gateway as a File Server in the cloud. In this case, files are stored in S3. For your exam, remember that it uses Network File System (NFS) and Server Message Block (SMB). If a question asks about File storage in relation to Storage Gateway, or mentions NFS or SMB, the answer is most likely File Gateway.

When you see references to NFS or SMB in the AWS Certified Solutions Architect – Associate exam, the answer is most likely File Gateway

When you see references to NFS or SMB in the AWS Certified Solutions Architect – Associate exam, the answer is most likely File Gateway

Tape Gateway

Tape Gateway deals with backups. Before the cloud and Network Attached Storage (NAS) devices, tapes were used to back up servers.

"A tape gateway provides cloud-backed virtual tape storage. The tape gateway is deployed into your on-premises environment as a VM running on VMware ESXi, KVM, or Microsoft Hyper-V hypervisor."

Think of Tape Gateway as storing the contents of physical backup tapes with data backed up into either S3, Glacier, or Glacier Deep Archive.

On the exam, if you see a question related to Storage Gateway and tapes, Tape Gateway is a likely answer.

AWS Tape Gateway is a virtual tape library (VTL) interface

AWS Tape Gateway is a virtual tape library (VTL) interface

Volume Gateway

When a question asks about file storage, NFS or SMB, think File Gateway. When a question asks about backup tapes, think Tape Gateway. When a question asks about iSCSI (Internet Small Computer System Interface), think Volume Gateway.

Here is an AWS description:

"You can configure the AWS Storage Gateway service as a Volume Gateway to present cloud-based iSCSI block storage volumes to your on-premises applications."

What makes Volume Gateway confusing is that it comes in two different types.

  • Stored Volumes
  • Cached Volumes

Stored Volumes

The easiest way to understand Stored Volumes is to think of a smartphone. Smartphones generally back up everything into the cloud. An iPhone will back up data into iCloud. An iPhone user generally doesn't interact with iCloud for day-to-day usage. What they use, Contacts, eBooks, or downloaded music, is mostly on their phone. But if they upgrade their phone, they can log into their account on the new phone, and then their data like Contacts will download to their new phone. They can also download photos, documents, etc. to the new phone.

Stored Volumes are similar in that all data is stored on-premises. Users accessing that data are accessing it on-premises. The data going into the AWS cloud is for backup purposes.

Here is how AWS describes it:

"If you need low-latency access to your entire dataset, first configure your on-premises gateway to store all your data locally. Then asynchronously back up point-in-time snapshots of this data to S3. This configuration provides durable and inexpensive offsite backups that you can recover to your local data center or EC2. For example, if you need replacement capacity for disaster recovery, you can recover the backups to EC2."

Stored Volumes are designed for disaster recovery. If an on-premises storage device becomes corrupted, that data can then be accessed from S3.

Cached Volumes

For Cached Volumes, think of a Chromebook. A Chromebook is a laptop with limited local storage. It's designed for use with cloud-based services like Gmail, YouTube, and Google Docs. Instead of downloading software, a Chromebook uses Android apps.

Cached Volumes are similar in that most data is stored in AWS S3. Only data that's used frequently is stored (or cached) on-premises. Just like a Chromebook doesn't need much local storage, using Cached Volumes don't require as much on-premises storage.

"You store your data in S3 and retain a copy of frequently accessed data subsets locally. Cached volumes offer a substantial cost savings on primary storage and minimize the need to scale your storage on-premises. You also retain low-latency access to your frequently accessed data."

What Is AWS Storage Gateway?

Summary

Volume Gateway:

For your exam, remember that Stored Volumes store all data both on-premises and in the cloud. Data is backed up largely for Disaster Recovery (DR) if on-premises storage is no longer available for some reason. All data is kept on-premises.

Cached Volumes store all data in the cloud. Only frequently accessed data is cached on-premises. Only frequently accessed data is kept on-premises.

For the exam, pay attention to the scenario in each question. If data is being stored and used on-premises but backed up into the cloud, that's Stored Volumes. If a company wants to minimize on-premises storage costs by storing only frequently accessed data while keeping everything else in the cloud, that's Cached Volumes.

Tape Gateway:

Tape Gateway is a virtualized version of physical tape cartridges.

File Gateway:

File Gateway uses the NFS or SMB protocols. Look for the word 'file' in an exam question.

References:

I've deliberately simplified this information to make it easy to understand. You should read the following before you take your exam to get a more in-depth description of each option:

https://docs.aws.amazon.com/storagegateway/latest/userguide/WhatIsStorageGateway.html

https://docs.aws.amazon.com/storagegateway/latest/userguide/StorageGatewayConcepts.html

https://aws.amazon.com/storagegateway

Introducing AWS Storage Gateway

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

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