SOA-C02 Reliability and Business Continuity Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  Stop the EC2 instance before taking the snapshot.

  Why it's wrong here

  Stopping the EC2 instance is a valid but unnecessarily heavy way to make a consistent snapshot, since it forces all processes to terminate and removes the instance from production for the entire backup window. This causes avoidable downtime for any service being served. Using a filesystem freeze achieves the same crash-consistent snapshot while keeping the instance fully online, so stopping is not the correct approach.

• ✗

  Take a snapshot directly from the attached volume without any preparation.

  Why it's wrong here

  Taking a snapshot directly from an attached, active volume without any preparation does not guarantee consistency. The filesystem's page cache may hold recently written blocks that have not yet reached the disk, and in-flight I/O can leave the snapshot with a mix of old and new data. This can produce a corrupted or incomplete backup when restored, especially for filesystems that require journal replay to reach a valid state.

• ✗

  Detach the volume from the instance before taking a snapshot.

  Why it's wrong here

  Detaching the volume before snapshotting forces a filesystem unmount, which is itself a form of downtime and can fail if the filesystem is busy or the application holds open files. For a root volume, detaching is impossible while the instance is running and would require a full stop, defeating the purpose of an online backup. This approach adds operational risk and is entirely unnecessary because a properly frozen filesystem on a running instance yields a safe snapshot.

• ✓

  Take a snapshot of the EBS volume after freezing.

  Why this is correct

  Taking a snapshot immediately after freezing the filesystem ensures the on-disk state is a stable, point-in-time representation. The freeze command flushes all dirty buffers and suspends new write operations, so the snapshot includes every block in a coherent relationship with the filesystem journal. This produces a crash-consistent backup without any interruption to the instance or application, making it the recommended backup method.

• ✓

  Freeze the filesystem and flush I/O operations using a tool like fsfreeze.

  Why this is correct

  fsfreeze (or xfs_freeze on XFS) suspends all new filesystem access, flushes pending writes and metadata, and leaves the volume in a state that exactly matches what a power loss would produce. After the snapshot completes, unfreezing resumes normal I/O operations seamlessly. This is the standard Linux practice for obtaining a reliable, crash-consistent EBS snapshot from a mounted volume without restarting or stopping services.

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