Tracking EC2 Linux Coverage: A Strategic Cost Analysis Guide

This guide demonstrates how to calculate EC2 Linux coverage—the percentage of compute spend on Linux versus Windows instances—using AWS Cost and Usage Reports to identify optimization opportunities that typically reduce EC2 costs through data-driven OS selection strategies. Linux instances cost 20-40% less than equivalent Windows instances.

Note for CUDOS Dashboard Users

If you're already using the CUDOS dashboard, this information is readily available in the Compute section under "EC2 Normalized Hours by Platform." You can directly view your Linux coverage metrics without running custom queries. The dashboard provides an intuitive visualisation of your operating system distribution and associated costs, making it easier to track your Linux coverage targets and identify optimization opportunities.

Why Linux Coverage Matters for your AWS Bill

Understanding your EC2 operating system distribution isn't just about inventory—it's about strategic cost optimization. Linux instances typically cost 20-40% less than Windows instances due to licensing differences, making Linux coverage a key metric for cloud financial management.

What This Analysis Reveals

Linux Coverage = (Linux EC2 Spend ÷ Total EC2 Spend) × 100

This metric helps you:

• Identify cost optimization opportunities - Higher Linux coverage typically means lower overall costs
• Track migration progress - Monitor Windows-to-Linux migration initiatives
• Benchmark against industry standards - Most cloud-native companies achieve 70-85% Linux coverage
• Support budget planning - Predict cost impact of OS strategy changes

Use Cases

1. Cost Optimization Teams

Track the financial impact of OS choices and identify non-Linux workloads.

2. Cloud Architects

Validate that new applications are defaulting to cost-effective Linux instances.

3. Finance Teams

Understand cost drivers and forecast savings from OS standardization initiatives.

4. Migration Planning

Monitor progress of Windows-to-Linux migration projects with quantifiable metrics.

The Query

-- AWS Cost and Usage Report (CUR) 2.0 Query
-- Analyzes EC2 costs split by Linux vs Windows operating systems

SELECT
    bill_billing_period_start_date,
    bill_payer_account_id,
    -- Calculate total EC2 Linux costs (excluding Windows)
    SUM(CASE WHEN ec2_filter = 1 AND product_operating_system NOT LIKE '%Windows%'
        THEN cost_amount ELSE 0 END) AS "EC2 Linux spend ($)",
    -- Calculate total EC2 Windows costs
    SUM(CASE WHEN ec2_filter = 1 AND product_operating_system LIKE '%Windows%'
        THEN cost_amount ELSE 0 END) AS "EC2 Windows spend ($)",
    -- Calculate Linux percentage of total EC2 spend
    CASE WHEN SUM(CASE WHEN ec2_filter = 1 THEN cost_amount ELSE 0 END) > 0
        THEN ROUND(SUM(CASE WHEN ec2_filter = 1 AND product_operating_system NOT LIKE '%Windows%'
            THEN cost_amount ELSE 0 END) * 100.0 / 
            SUM(CASE WHEN ec2_filter = 1 THEN cost_amount ELSE 0 END), 1)
        ELSE NULL
    END AS "Linux Coverage"
FROM (
    SELECT 
        bill_billing_period_start_date,
        bill_payer_account_id,
        product_operating_system,
        -- Filter for EC2 RunInstances usage (excludes data transfer and tax)
        CASE WHEN line_item_line_item_type NOT IN ('Tax')
            AND product_product_name = 'Amazon Elastic Compute Cloud'
            AND product_operation LIKE '%RunInstances%'
            AND line_item_product_code <> 'AWSDataTransfer'
            AND line_item_usage_type NOT LIKE '%DataXfer%'
            -- Include on-demand, Savings Plans, and Reserved Instance usage
            AND line_item_line_item_type IN ('Usage', 'SavingsPlanCoveredUsage', 'DiscountedUsage')
            THEN 1 ELSE 0 END AS ec2_filter,
        -- Calculate effective cost based on pricing model
        CASE 
            WHEN line_item_line_item_type = 'Usage' THEN line_item_unblended_cost  -- On-demand cost
            WHEN line_item_line_item_type = 'SavingsPlanCoveredUsage' THEN savings_plan_savings_plan_effective_cost  -- SP effective cost
            WHEN line_item_line_item_type = 'DiscountedUsage' THEN reservation_effective_cost  -- RI effective cost
            ELSE 0
        END AS cost_amount
    FROM {your_cur_table}
    WHERE bill_billing_period_start_date >= DATE('2025-01-01')  -- Filter for 2025 onwards
) filtered
GROUP BY bill_billing_period_start_date, bill_payer_account_id
ORDER BY bill_billing_period_start_date, bill_payer_account_id ASC;

Pro Tip: Replace {your_cur_table} with the your actual database and table names. Update the year and month parameters to match the desired analysis period.

Key Query Features

Cost entries considered in the query

• On-Demand Usage - Standard hourly billing
• Savings Plans - Committed usage discounts
• Reserved Instances - Capacity reservations
• Excludes - Data transfer and non-compute costs

Interpreting Results

Linux Coverage	Interpretation	Action
85%+	Excellent optimization	Maintain current strategy
70-84%	Good coverage	Identify remaining Windows workloads
50-69%	Moderate	Prioritize migration assessment
<50%	High cost exposure	Optimization needed

Implementation Steps

1. Set up the query in Amazon Athena using your Cost and Usage Report
2. Create a dashboard to track trends over time
3. Set alerts for coverage drops below target thresholds
4. Share reports with stakeholders monthly

Expected Outcomes

Organizations typically see:

• 15-30% EC2 cost reduction by increasing Linux coverage
• Improved cost predictability through standardization
• Faster deployment cycles with Linux-first policies
• Enhanced security posture through reduced attack surface

Next Steps

• Establish baseline Linux coverage metrics
• Set target coverage goals (recommend 75%+)
• Identify Windows workloads suitable for migration
• Track progress monthly and adjust strategies accordingly

This analysis transforms raw billing data into actionable insights, enabling data-driven decisions about your cloud infrastructure strategy.

Conclusion

Linux coverage analysis isn't just a reporting exercise—it's a strategic tool that directly impacts your bottom line. With potential savings from Linux instances costing 20-40% less than equivalent Windows instances on EC2 costs and the ability to track optimization progress in real-time, this metric should be part of every cloud team's monthly review.

Start today: Run the query against your Cost and Usage Report, establish your baseline, and begin identifying quick wins. Don't let licensing costs silently drain your cloud budget—take control with data-driven OS strategy decisions.