PCDE Practice Question: Manage a solution that can span multiple database technologies
A Bigtable cluster is configured with SSD storage. The team needs to reduce costs by switching to HDD storage while maintaining the same cluster ID and node count. What is the correct approach?
⚠ Common exam trap
Google often tests the immutability of Bigtable storage type and the misconception that you can simply update it via the console or CLI, leading candidates to choose options A or D.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a new Bigtable instance with HDD storage, then use a table export/import to move data.
Bigtable does not allow in-place modification of storage type (SSD vs. HDD) on an existing cluster. To switch storage, you must create a new instance with HDD storage and migrate data using export/import (e.g., via Cloud Storage and Dataflow). Option C correctly describes this process, preserving the cluster ID and node count by recreating the instance with the same configuration but HDD storage.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Edit the cluster settings and change the storage type from SSD to HDD.
Why it's wrong here
Storage type cannot be changed on an existing cluster.
- ✗
Delete the cluster and recreate it with HDD storage.
Why it's wrong here
This would lose data unless backed up.
- ✓
Create a new Bigtable instance with HDD storage, then use a table export/import to move data.
Why this is correct
A new cluster with HDD storage is required; data can be migrated via export/import.
- ✗
Use gcloud bigtable instances update to change the storage type.
Why it's wrong here
No such command exists for storage type change.
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Same concept, more angles
4 more ways this is tested on PCDE
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Variation 1. A company runs a Cloud Bigtable instance with SSD storage and wants to switch to HDD storage to reduce costs. The instance cannot tolerate downtime for data migration. What is the correct approach?
medium- ✓ A.Create a new Cloud Bigtable cluster with HDD storage and migrate data
- B.Increase the number of nodes to reduce per-node cost
- C.Add a cross-region replica and then promote it with HDD storage
- D.Use the gcloud bigtable clusters update command to change storage type
Why A: Cloud Bigtable does not support in-place conversion of storage type from SSD to HDD. The only way to switch storage without downtime is to create a new cluster with HDD storage, then use a replicated setup (e.g., via a replication cluster or application-level dual-write) to migrate data while the original cluster remains operational. This ensures zero downtime during the migration.
Variation 2. A financial services company uses Cloud Bigtable for real-time fraud detection. They have a cluster with 10 nodes using HDD storage and are experiencing high latency due to disk throughput bottlenecks. They need to improve performance with minimal downtime. What should they do?
hard- A.Modify the existing cluster's storage type to SSD via the Cloud Console
- ✓ B.Create a new cluster with SSD storage, replicate data, then update the application to point to the new cluster
- C.Use Cloud Bigtable's hot tablet detection to rebalance the data
- D.Increase the number of nodes in the existing cluster
Why B: Cloud Bigtable does not support in-place conversion of storage from HDD to SSD. The only way to migrate to SSD storage is to create a new cluster with SSD, replicate data using Bigtable replication, and then update the application connection string to point to the new cluster. This approach minimizes downtime by allowing the old cluster to serve reads during replication.
Variation 3. A Cloud Bigtable cluster is currently using HDD storage. The team wants to switch to SSD for better performance. What is the correct approach?
medium- ✓ A.Create a new cluster in the same instance with SSD, then delete the old HDD cluster.
- B.Use the gcloud bigtable clusters update command with the --storage-type flag.
- C.Export the table to Cloud Storage, delete the instance, create a new one with SSD, and import.
- D.Delete the existing cluster and recreate it with SSD. Data is retained in the instance.
Why A: In Cloud Bigtable, storage type is a property of the cluster, not the instance. You cannot change the storage type of an existing cluster. The correct approach is to add a new cluster with SSD storage to the same instance, then delete the original HDD cluster. This allows you to migrate without data loss or downtime, as data is replicated across clusters in the same instance.
Variation 4. A company has a Cloud Bigtable cluster using HDD storage. They are migrating to a workload that requires lower latency, so they need to switch to SSD storage. How should they accomplish this?
hard- A.Add more nodes to the existing cluster to improve latency.
- B.Export data to Avro files, create a new SSD cluster, and import the data.
- C.Modify the existing cluster's storage type to SSD using the Cloud Console.
- ✓ D.Create a new Bigtable cluster with SSD storage in the same instance, replicate data, then delete the old cluster.
Why D: Cloud Bigtable does not support in-place conversion of storage type from HDD to SSD. The proper migration path is to create a new cluster with SSD storage within the same instance, enable replication to keep data synchronized, and then delete the old HDD cluster. This approach minimizes downtime and ensures data consistency.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PCDE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCDE exam.