Large Database Migration over Slow Network Using Snowball and DMS
A company is migrating a 10 TB PostgreSQL database from on-premises to Amazon RDS for PostgreSQL. They need to minimize downtime and have limited network bandwidth. Which approach is most appropriate?
Quick Answer
The correct approach is to use AWS Snowball to transfer a physical backup for the initial load, then AWS DMS for ongoing replication. This combination directly addresses the challenge of migrating a large database over a slow network by offloading the bulk data transfer to Snowball’s physical shipping, which bypasses bandwidth constraints entirely. After the Snowball data is loaded into Amazon RDS for PostgreSQL, DMS handles the minimal remaining changes via change data capture, keeping downtime to a near-zero window. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of hybrid migration strategies where network speed is the bottleneck—a common trap is choosing DMS alone for the full load, which would take prohibitively long over limited bandwidth. Remember the memory tip: “Snowball for the big haul, DMS for the final call.”
⚠ Common exam trap
It's easy for candidates to assume DMS can handle any data volume over any network, ignoring the practical reality that large datasets (e.g., 10 TB) over limited bandwidth require a physical transfer mechanism like Snowball to avoid days or weeks of migration time.
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
✓
Use AWS Snowball to transfer a physical backup to AWS, then use DMS for ongoing replication.
The 10 TB database size combined with limited network bandwidth makes a direct online migration impractical due to prolonged transfer times. AWS Snowball allows you to physically ship the database backup to AWS, bypassing bandwidth constraints. After loading the backup into Amazon RDS, AWS DMS can perform ongoing change data capture (CDC) replication to synchronize any changes made during the transfer, minimizing downtime.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use AWS Database Migration Service (DMS) with a full load and ongoing replication to keep the target in sync.
Why it's wrong here
Full load over limited bandwidth may take too long; initial load should be done offline.
- ✗
Use pg_dump to export the database and pg_restore to import to RDS, then use DMS for replication.
Why it's wrong here
pg_dump/pg_restore requires downtime; not minimal downtime.
- ✓
Use AWS Snowball to transfer a physical backup to AWS, then use DMS for ongoing replication.
Why this is correct
Snowball handles the large initial load offline; DMS handles ongoing changes with minimal bandwidth.
- ✗
Use AWS Direct Connect to increase bandwidth and then use DMS for full load and replication.
Why it's wrong here
Direct Connect may not be available or may take time to provision; Snowball is more immediate.
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Same concept, more angles
2 more ways this is tested on DBS-C01
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is migrating a 50 GB PostgreSQL database from on-premises to Amazon RDS for PostgreSQL. The network bandwidth between on-premises and AWS is 50 Mbps. The migration must complete within 24 hours. What is the most efficient way to transfer the initial data?
medium- A.Use AWS Snowball to physically transfer the database backup to AWS, then load into RDS.
- B.Use AWS DMS to perform a full load directly over the internet.
- C.Set up a VPN connection and use AWS DMS with ongoing replication.
- ✓ D.Use pg_dump to export the database and upload to S3 via the internet, then restore into RDS.
Why D: The most efficient method is to use pg_dump to export the database, upload the dump file to Amazon S3 via the internet (or using AWS CLI with multipart upload), and then restore it into Amazon RDS for PostgreSQL. Given the database size of 50 GB and a 50 Mbps link, the theoretical transfer time is about 2.3 hours, and even with realistic overhead and retransmissions, it can complete well within the 24-hour window. This approach avoids the shipping delay and logistical overhead of AWS Snowball, which would take several days to arrive and process.
Variation 2. A company is migrating a 3 TB SQL Server database to Amazon RDS for SQL Server. They have limited network bandwidth (100 Mbps) and need to complete the migration within 3 days. Which two approaches could meet the requirements? (Choose TWO.)
hard- A.Export the database to a flat file, compress it, and upload to S3 via the internet, then import into RDS.
- B.Use AWS DataSync to transfer the database files directly to Amazon S3.
- ✓ C.Use AWS Snowball to physically transfer a full database backup to AWS, then restore into RDS.
- ✓ D.Use AWS DMS with ongoing replication to perform a full load over the internet and then continuously replicate changes until cutover.
- E.Establish a VPN connection and use AWS DMS with full load only.
Why C: AWS Snowball provides a physical appliance that can transfer the 3 TB database backup offline, bypassing the 100 Mbps bandwidth limitation entirely. The full backup can be restored into RDS for SQL Server using the native restore process, making it feasible within the 3-day window. Option D is correct because AWS DMS with ongoing replication can perform the initial full load over the internet; at 100 Mbps, the full load of 3 TB takes approximately 2.78 days, which is within the 3-day window. Ongoing replication then captures changes until cutover, ensuring data consistency and minimal downtime.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DBS-C01 practice question is part of Courseiva's free Amazon Web Services 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 DBS-C01 exam.