How to Seamlessly Migrate AWS EC2 Instances to Google Cloud with Minimal Downtime

Modern multi-cloud strategies demand more than a basic lift-and-shift. Real value comes from re-platforming to cloud-native architecture—without losing sight of uptime and operational sanity. Migrating a production EC2 workload to GCP is rarely a one-button affair, especially when minimizing disruption is non-negotiable.

1. Inventory & Dependency Mapping

First step—map reality, not wishful thinking.

Checklist:

• EC2 instance types/allocation (CPU, RAM, EBS volume details, AMI IDs)
• Dependent services (RDS, S3, ALB/NLB, IAM Role policies)
• Network footprint (VPC IDs, subnets, security groups, route tables, VPC peering)
• Application dependencies: overlay monitoring (e.g., CloudWatch agents), backup agents, licensing

A sample asset inventory (as CSV) helps spot at-risk workloads:

InstanceId,Name,Type,Zone,Role,DependsOn,AMI
i-0abc,prod-api-1,m5.large,us-east-1a,api,RDS-db1,ami-0dead

Pitfall: Dependencies on platform-attached resources (e.g., S3-backed config, IAM secrets retrieval) require design decisions—don't expect them to translate 1:1.

2. Preparing Google Cloud

1. Project setup: Create distinct GCP projects per environment (dev, prod).

2. Enable billing, APIs: Compute Engine, IAM, Cloud Storage, and relevant network APIs.

3. Replicate networking: VPC, subnets (match CIDRs for smooth cutover), and firewall—Google’s firewall rules map 1:1 to VM tags, not IPs.

   AWS	GCP Equivalent
   Security Group	Ingress/Egress Firewall
   VPC Subnet	VPC Subnet

4. Service accounts: Prefer least-privilege for automation, distinctly for import tooling.

   Side note: Both Deployment Manager and Terraform >=1.2.0 (google provider >=4.0) automate infra provisioning, but beware of IAM propagation delays.

3. Migrating the VM Image

GCP offers two practical options:

Option A — Migrate for Compute Engine

Use Google Migrate for Compute Engine:

• Automated agentless workload discovery.
• Performs continuous replication ("Staging" mode), allowing you to cut over with near-zero downtime.
• Supports Windows Server 2019, RHEL 8.x, Ubuntu LTS, and CentOS 7+.

Known gotcha: Highly-customized Amazon Linux 2 images may hit kernel compatibility issues; migrate with caution.

Option B — Manual Image Export/Import

For controlled, stepwise migrations or less dynamic instances:

1. Create Amazon Machine Image (AMI) from source EC2 root volume.

2. Export snapshot to S3 as a raw disk (must use external bucket, not EBS).

3. Copy exported .raw or .vmdk to GCP Storage:

   aws ec2 export-image \
     --image-id ami-0deadbeef \
     --disk-image-format RAW \
     --s3-export-location S3Bucket=my-export-bucket,S3Prefix=exports/
   

4. Import to GCP as a custom image (using gcloud CLI):

   gsutil cp s3://my-export-bucket/exports/myimage.raw gs://my-gcp-bucket/
   gcloud compute images import aws-legacy-image \
     --source-file gs://my-gcp-bucket/myimage.raw \
     --os ubuntu-1804
   

5. VM launch: Boot a new Compute Engine instance with this custom image.

Critical: Amazon Linux, cloud-init scripts, and udev network naming conventions often diverge from GCP's setup, requiring manual adaptation.

4. Data Consistency & Database Edge Cases

Database (RDS/Aurora → GCP Cloud SQL or self-managed):

• For MySQL/Postgres: Database Migration Service (DMS) handles continuous/one-off replication.

• In scenarios where DMS is unsupported (e.g., Aurora specific-engine extensions), revert to logical dumps:

  mysqldump --databases myapp --single-transaction --set-gtid-purged=OFF > myapp.sql
  gsutil cp myapp.sql gs://gcp-import/
  gcloud sql import sql mycloudsql-instance gs://gcp-import/myapp.sql
  

• For storage: Use rsync -az --delete either over a VPN peering or via intermediary storage.

Non-obvious tip: Some legacy AWS EBS-backed tools use device labels not recognized on GCP (/dev/xvda → /dev/sda1). Remap or manually correct /etc/fstab to avoid boot failures.

5. DNS, Networking, and Cutover

Don't rely on long DNS TTLs vanishing overnight—update records 48h prior to migration. Use TTL=60 for active records.

• Allocate static external IPs on GCP well before cutover (some outdated docs refer only to ephemeral IPs).
• Cutover: Use a GCP HTTP(S) Load Balancer in front of migrated VMs. If your infra requires sticky sessions, configure x-google-backend with sessionAffinity.

Quick ASCII network before/after:

[User] -> [AWS ALB] -> [EC2 Pool]       (Before)
[User] -> [GCP HTTPS LB] -> [GCE IG]   (After)

During sync: Dual-write period if application semantics allow, else, tightly choreograph the freeze and switch.

6. Validation & Testing

• Deploy test traffic via a controlled header or host override.
• Validate firewall and routing (GCP egress rules frequently block outbound SMTP by default).
• Scrutinize instance logs (/var/log/syslog) post-migration for Failed to start or No such device errors.

Smoke test, then ramp up real traffic with shadowing where possible.

7. Go-Live & Post-Migration Execution

Monitor via Google Cloud Operations (Stackdriver). Expect metric drift—CPU utilization may differ under equivalent loads due to underlying hardware generation (e.g., N2 vs T3).

Only decommission AWS artifacts when stability is demonstrated (typical confidence window: 2-7 days depending on workload criticality).

Optimization passes:

• Evaluate pd-ssd vs pd-standard disk classes for IOPS-sensitive workloads.
• Use preemptible VMs or committed use discounts for predictable, stateless fleet members.
• Layer GCP-native services: Cloud Pub/Sub vs SNS, Memorystore vs ElastiCache, BigQuery as Athena alternative, etc.

Note: For enterprise fleets, consider building a canary pipeline for GCP deployments using your existing CI/CD (Jenkins, GitLab, or Cloud Build), integrating smoke tests before global traffic switch.

Summary Table: Essential Migration Primitives

Migrating production EC2 workloads to GCP isn’t “push a button and pray”. Each phase—from forensic asset cataloging, custom image export quirks, to database zero-downtime test runs—demands engineering discipline. GCP migration tools help, but experienced ops teams devote real attention to network, data, and post-migration tuning. In some corners, brute-force lift-and-shift can work; long term, decoupling to GCP-native services reduces headaches.

Other gotchas? Cold-start times on first-booted imported images (up to 40 seconds); IAM role mismatches during automation; invisible egress blocks for legacy mail flows.

Questions or real-world horror stories welcome. Tried-and-true scripts and reference architectures beat “cloud magic” every time.

References & Tools:

• Google Migrate for Compute Engine
• Google Database Migration Service
• Terraform Google Provider
• GCP image import docs
• AWS VM Import/Export docs