Amazon RDS databases often have storage volumes that are significantly larger than necessary, resulting in wasted cloud spend. The RDS Optimize Storage Finder identifies opportunities to right-size your RDS storage volumes without impacting performance or future growth requirements. By implementing these recommendations, you can reduce your RDS storage costs while maintaining appropriate capacity for your database workloads.

Contents

Overview

Problem Statement

Amazon RDS storage provisioning often follows a cautious approach: database administrators allocate more space than immediately needed to accommodate future growth, avoid capacity issues, and minimize maintenance windows. However, this proactive provisioning frequently results in significant over-allocation, with many databases using only a small fraction of their allocated storage over extended periods.

This over-provisioning creates several challenges:

  • Unnecessary costs for unused storage capacity
  • For GP2 volumes, excessive IOPS allocation (since IOPS scale with volume size)
  • Difficulty in accurately forecasting and controlling database infrastructure costs
  • Sunk capital in resources that provide no operational benefit

Unlike compute resources which can be easily downsized, RDS doesn’t natively support reducing storage allocation, making optimization more complex and often overlooked.

Solution

The RDS Optimize Storage Finder analyzes your RDS instances to identify databases with significantly over-provisioned storage volumes. It examines historical usage patterns, growth trends, and performance requirements to recommend optimal storage configurations without compromising performance or future capacity needs.

Key aspects of the solution include:

  • Identifying instances where allocated storage substantially exceeds actual usage
  • Analyzing storage type (GP2, GP3, IO1) to recommend the most cost-effective configuration
  • Ensuring adequate IOPS for performance-sensitive workloads
  • Recommending storage autoscaling to automatically handle future growth
  • Preserving a minimum 20% free space buffer after optimization

While RDS doesn’t allow direct storage downsizing, the Finder provides detailed guidance on creating a new instance with optimized storage and migrating your data, enabling significant long-term cost savings.

Benefits

By implementing the RDS Optimize Storage recommendations, you can achieve:

  • Substantial cost savings (typically 30-40%) on RDS storage expenses
  • Improved cost efficiency through optimized storage-to-usage ratios
  • Enhanced performance when migrating from GP2 to GP3 storage
  • Better alignment of resources with actual requirements
  • Simplified capacity management with autoscaling enabled
  • Greater visibility into database storage utilization

AWS Services Affected

Amazon RDS
Amazon RDS

How It Works

Finder Component

The RDS Optimize Storage Finder employs a multi-step analysis process to identify storage optimization opportunities:

  1. Database Discovery: Inventories all RDS instances across your AWS accounts
  2. Storage Analysis: Collects 31 days of storage utilization metrics from CloudWatch
  3. Growth Pattern Recognition: Analyzes historical data to identify usage trends and peak requirements
  4. Performance Evaluation: Reviews IOPS and throughput metrics to ensure optimization doesn’t impact performance
  5. Cost Impact Calculation: Estimates potential savings based on current vs. optimized storage configuration
  6. Threshold Filtering: Prioritizes opportunities where annual savings exceed the configured threshold (default $100)

For each identified opportunity, CloudFix provides detailed information including:

  • Database identifier and engine type
  • Current storage allocation and utilization metrics
  • Recommended optimal storage size
  • Suggested storage type (GP2, GP3, or IO1/IO2 based on performance needs)
  • Projected annual savings
  • Storage autoscaling recommendations

Optimization Process

Since Amazon RDS doesn’t support direct storage downsizing, optimizing over-provisioned RDS storage requires a migration approach. CloudFix provides a detailed, step-by-step implementation guide:

  1. Preparation Phase
    • Review CloudFix recommendations to select RDS instances for optimization
    • Schedule a maintenance window for the migration
    • Create a migration runbook specific to your database engine
  2. Create Optimized Instance
    • Provision a new RDS instance with the recommended storage configuration
    • Enable storage autoscaling with appropriate maximum threshold
    • If recommended, switch from GP2 to GP3 for better performance and lower cost
    • Configure the same security groups, parameter groups, and option groups as the original
  3. Data Migration
    • For MySQL or PostgreSQL: Use native tools like mysqldump/pg_dump or AWS DMS
    • For larger databases: Consider snapshot restoration with subsequent replication
    • For minimal downtime: Set up replication between old and new instances
  4. Validation & Cutover
    • Verify data integrity and application functionality with the new instance
    • Update connection strings or endpoints in your applications
    • Monitor performance metrics after the migration
  5. Cleanup
    • Retain the original instance temporarily as a backup
    • After confirming stability, schedule decommissioning of the original instance

For production databases, CloudFix recommends using AWS Database Migration Service (DMS) to minimize downtime during the migration process.

FAQ

Can Amazon RDS storage be reduced directly?

No, Amazon RDS doesn’t support direct reduction of allocated storage. This limitation stems from the underlying Amazon EBS volumes, which can only increase in size, not decrease. The only way to reduce storage is to create a new RDS instance with optimized storage and migrate your data.

How does CloudFix ensure that the recommended storage size is sufficient?

CloudFix analyzes 31 days of historical storage usage patterns and incorporates a 20% minimum free space buffer in all recommendations. Additionally, CloudFix recommends enabling storage autoscaling, which automatically increases storage when needed, preventing capacity issues as your database grows.

Will reducing storage impact my database performance?

For GP2 storage types, performance (IOPS) is directly tied to volume size. CloudFix takes this into consideration and ensures that recommended optimizations won’t reduce available IOPS below your workload requirements. In many cases, CloudFix recommends migrating to GP3, which decouples performance from storage size, allowing you to maintain or improve performance even with smaller volumes.

What is the difference between GP2 and GP3 storage, and why might CloudFix recommend switching?

GP2 storage allocates IOPS based on volume size (3 IOPS per GB), while GP3 allows independent provisioning of storage size, IOPS, and throughput. GP3 is generally 20% cheaper than GP2 for the same storage capacity and offers more predictable performance. CloudFix may recommend switching to GP3 when it provides the same or better performance at a lower cost.

How does RDS storage autoscaling work?

RDS storage autoscaling automatically increases your allocated storage when free space falls below 10% for at least 5 minutes. It’s designed to prevent storage-full scenarios that could impact database availability. Autoscaling increments are either 10% of current size, 5 GB, or projected 7-hour growth—whichever is largest. You configure a maximum threshold to control costs, and autoscaling never exceeds this limit.

What is the typical migration downtime when implementing these recommendations?

Downtime varies based on database size, migration method, and engine type. Small databases using dump/restore methods might require minutes to hours of downtime. Using AWS DMS with change data capture (CDC) can reduce downtime to seconds or minutes for the final cutover. For critical systems, you can implement replication-based approaches with minimal downtime, though these require more complex setup and testing.

Can CloudFix automatically implement these storage optimizations?

No, RDS Optimize Storage is a Finder-only feature that requires manual implementation. Since optimizing RDS storage involves creating new instances and migrating data—potentially impacting production systems—CloudFix provides recommendations and guidance but leaves the implementation to your database team to ensure proper testing and validation.