Choosing shared storage: SAA-C03 study notes and practice questions
What to know about Choosing shared storage for the SAA-C03 exam, from the Design High-Performing Architectures domain (24% of the exam guide), then 3 free questions to test it. Part of the SAA-C03 study guide.
Storage choice questions describe how data is accessed: by one server or many, over which protocol, with what latency. That description maps to one service.
The map
Need
Service
Block storage for one EC2 instance (boot volumes, databases)
Amazon EBS (Multi-Attach for io1/io2 is a narrow exception)
Shared file system for many Linux instances, containers or Lambda, NFS, scales automatically
Amazon EFS
Windows file shares (SMB) with Active Directory permissions
FSx for Windows File Server
High-performance computing or ML training, linked to S3, sub-millisecond
FSx for Lustre
NFS, SMB and iSCSI from one system, or moving NetApp workloads
FSx for NetApp ONTAP
Moving ZFS-based file servers, very low latency NFS
FSx for OpenZFS
Objects of any size, accessed over HTTPS by applications, unlimited scale
Amazon S3
Very fast temporary storage that can be lost
EC2 instance store
Key facts
EBS volumes live in one Availability Zone. To move one, take a snapshot and create a volume in another zone.
EFS Regional file systems store data across multiple zones with a mount target in each, and grow and shrink automatically. One Zone file systems cost less but don’t survive a zone failure. Elastic throughput removes throughput planning.
EFS storage classes (Standard, Infrequent Access, Archive) with lifecycle management cut cost for files that cool down.
FSx for Windows File Server Multi-AZ survives a zone failure; Single-AZ doesn’t.
FSx for Lustre has scratch deployments (cheapest, no replication, for temporary data you can rebuild from S3) and persistent deployments (replicated within a zone, for longer-lived data).
Mountpoint for Amazon S3 lets Linux applications read S3 like files, but it’s not a full POSIX file system.
Common traps
EBS for shared access. Most volumes attach to one instance; use EFS or FSx for sharing.
EFS for Windows. EFS is NFS for Linux; Windows needs FSx for Windows File Server.
Persistent FSx for Lustre for short jobs where data can be rebuilt from S3. Scratch is cheaper.
S3 when the application needs file locking or in-place edits. That’s a file system.
A media company runs a content management system on Linux EC2 instances in an Auto Scaling group across three Availability Zones.
Every instance must read and write the same set of files at the same time, using standard Linux file permissions and file locking. The files total 300 GB today but grow unpredictably, and the team does not want to manage storage capacity. The files must stay available if one Availability Zone fails.
Which storage option meets these requirements?
Choose one answer.
AA. An Amazon EBS io2 volume with Multi-Attach turned on, attached to every instance in the Auto Scaling group.
BB. An Amazon EFS Regional file system with mount targets in all three Availability Zones, mounted on every instance.
CC. An Amazon FSx for Lustre Persistent SSD file system with provisioned storage, mounted on every instance in the group.
DD. An Amazon FSx for Windows File Server Multi-AZ file system, mounted over SMB on every instance with cifs-utils.
B. Right: Correct. EFS is a managed NFS file system that many Linux instances can share at once. A Regional file system stores data across several Availability Zones, so it survives the loss of one, and it grows and shrinks automatically as files are added and removed. Learn more: What is Amazon Elastic File System? (opens in a new tab)
D. Wrong: Linux clients can mount FSx for Windows File Server over SMB, and Multi-AZ covers a zone failure. However, file permissions are Windows ACLs, so the application's standard Linux permissions are not stored natively. A Linux-native NFS file system fits better. Learn more: Accessing your data (opens in a new tab)
Explanation
Three needs decide it: shared read-write access with Linux semantics, survival of a zone failure, and no capacity planning. Amazon EFS Regional file systems meet all three, with mount targets in each Availability Zone and elastic storage. EBS Multi-Attach is limited to one zone, FSx for Lustre SSD is single-zone and provisioned, and FSx for Windows File Server uses Windows permissions.
A research team runs a weekly 8-hour genomics job across 400 Linux EC2 instances.
The input data lives in Amazon S3, which holds the permanent copy, and the results must be written back to S3. During the job, all instances need a shared POSIX file system that they can read and modify at the same time, with consistent sub-millisecond latency. If the file system fails mid-job, the team can simply rerun the job.
Which storage option meets these requirements MOST cost-effectively?
Choose one answer.
AA. An Amazon FSx for Lustre scratch file system linked to the S3 bucket, created for each run and deleted after results are exported.
BB. An Amazon FSx for Lustre persistent file system linked to the S3 bucket, left running between the weekly runs to keep data loaded.
CC. An Amazon EFS file system with Elastic throughput, loaded from the S3 bucket by AWS DataSync before each run and mounted on every instance.
DD. Mountpoint for Amazon S3 installed on every instance, mounting the bucket directly so the job reads and writes objects as files.
Show the answer and explanation
Answer: A
A. Right: Correct. FSx for Lustre on SSD storage gives sub-millisecond latency and very high aggregate throughput, and a linked file system presents S3 objects as files and can write results back to S3. Scratch file systems do not replicate data, which makes them the cheaper choice for short jobs whose data is safe in S3 and that can be rerun. Learn more: Deployment and storage class options for FSx for Lustre file systems (opens in a new tab)
B. Wrong: A persistent file system meets the performance needs and replicates data to survive server failures. That durability is not needed here because S3 holds the permanent copy, and keeping the file system running all week adds cost. A scratch file system per run is cheaper. Learn more: Linking your file system to an Amazon S3 bucket (opens in a new tab)
C. Wrong: EFS is a shared POSIX file system, but its best-case latency is about 1 ms for reads and 2.7 ms for writes, so it does not give consistent sub-millisecond latency. Copying the data in and out with DataSync also adds steps that a linked FSx for Lustre file system avoids. Learn more: Amazon EFS performance specifications (opens in a new tab)
D. Wrong: Mountpoint gives high-throughput access to S3 objects as files and costs nothing extra, but it cannot modify existing files and does not support file locking. It does not meet the need for a shared file system that the instances can read and modify concurrently. Learn more: Mount an Amazon S3 bucket as a local file system (opens in a new tab)
Explanation
The job needs a shared, fully POSIX file system with sub-millisecond latency, linked to S3, for a few hours a week, and the data can be rebuilt from S3. FSx for Lustre is built for this kind of HPC work, and the scratch deployment type is the lower-cost option for temporary, rerunnable processing. EFS is too slow for the latency target, and Mountpoint cannot modify existing files.
A company is moving a Windows-based document management application to AWS.
The application servers use shared folders over the SMB protocol, and folder permissions are controlled by groups in Microsoft Active Directory, which will run in AWS Directory Service for Microsoft Active Directory. The file share must stay available if an Availability Zone fails, and the IT team does not want to patch or manage file servers.
Which storage solution meets these requirements?
Choose one answer.
AA. An Amazon EFS file system using Regional storage, mounted on the Windows application servers in two Availability Zones.
BB. An Amazon FSx for Windows File Server Single-AZ file system joined to the directory, with daily automatic backups to restore from.
CC. Two Windows Server EC2 instances in different Availability Zones, joined to the directory and kept in sync with DFS Replication.
DD. An Amazon FSx for Windows File Server Multi-AZ file system joined to the AWS Managed Microsoft AD directory.
Show the answer and explanation
Answer: D
A. Wrong: EFS stores data across several Availability Zones, but it is an NFS file system and is not supported on Windows instances. It also does not use Active Directory groups for SMB share permissions. Learn more: Use Amazon EFS with Amazon EC2 (opens in a new tab)
C. Wrong: This can provide SMB shares that survive a zone failure, but the team would have to patch, back up and monitor the Windows file servers themselves. That breaks the requirement not to manage file servers.
D. Right: Correct. FSx for Windows File Server is a fully managed Windows file system that serves SMB shares and uses Active Directory for authentication and permissions. The Multi-AZ deployment runs a standby file server in a second zone and fails over automatically, usually in under 30 seconds. Learn more: What is FSx for Windows File Server? (opens in a new tab)
Explanation
The requirements are SMB shares with Active Directory permissions, survival of an Availability Zone failure, and no file servers to manage. FSx for Windows File Server Multi-AZ meets all three. Single-AZ does not survive a zone outage, EFS does not support Windows, and self-managed Windows servers bring the patching work the team wants to avoid.
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