Google Cloud offers a variety of discount pricing models to help manage and optimize cloud costs, including committed use discounts (CUDs), sustained use discounts (SUDs), Spot VMs, and special agreements. Among these, CUDs and SUDs stand out for their potential savings but cater to different usage patterns.
While they might seem similar, the differences between them are significant. To maximize your cloud investment, it’s essential to understand these fundamental differences.
This article details the differences between CUDs and SUDs and explores how these options can transform your approach to Google Cloud cost management.
What are committed use discounts (CUDs)?
Committed use discounts (CUDs) are a Google Cloud discounting option that allow users to receive significant discounts on their cloud resources in exchange for committing to a specific level of usage over a set period, typically one or three years. By committing to CUDs, businesses can benefit from reduced rates compared to on-demand pricing, making them an effective strategy for cost optimization in predictable and steady-state workloads.
There are two types of committed use discounts on Google Cloud:
- Resource-based CUDs: You commit to using a minimum amount of specific resources, such as vCPUs or memory, for a certain period. These CUDs focus on the quantity of compute resources you commit to using within a specific region and machine series. Resource-based CUDs only cover Google Cloud’s Compute Engine. You can commit to using hardware resources such as vCPUs, GPUs, or memory. With these commitments, you can receive discounts of up to 70% for memory-optimized machine types and up to 55% for other machine types.
- Spend-based CUDs: You commit to spending a minimum amount (measured in dollars per hour) over a specified term. One of the most significant benefits of spend-based CUDs is their flexibility, ensuring you’re not stuck paying for resources you no longer need. They cover a range of Google Cloud services, including Cloud Run, Kubernetes Engine (Autopilot), and Cloud SQL.
What are sustained use discounts (SUDs)?
Sustained use discounts (SUDs) are Google Cloud discounting options that automatically apply to your account when you consistently use resources over a defined percentage. These discounts are a great option for more flexible or unpredictable workloads, as they require no long-term commitment.
How do they work? If you use a Compute Engine resource, like virtual machines (VMs), for more than 25% of a billing month, you’re eligible for a discount. The more consistently the resource is used, the higher your savings — up to 30% savings on resources used for 100% of the month.
The discounts apply automatically — you don’t need to sign up or commit ahead of time. Every incremental hour beyond the 25% threshold gets a discount, making it a flexible and easy way to save.
Key differences between CUDs and SUDs
Understanding the differences between committed use discounts and sustained use discounts can help you make effective cloud cost optimization decisions. Both options offer valuable savings, but they cater to different needs and usage patterns.
Commitment and flexibility
CUDs require you to commit to using specific resources or spending a minimum amount over a set period: one or three years. Think of it as making a long-term pledge to use Google Cloud resources. This type of discount is ideal if you have predictable and steady usage patterns.
SUDs, on the other hand, provide flexibility as they automatically apply based on your usage without any long-term commitment. If your usage is sporadic or varies month to month, SUDs might be more suitable because they adjust according to your actual use.
Discount application
Depending on the term and commitment level, savings from CUDs can be huge. For example, you might get up to a 70% discount on VM instances when you commit to using them for three years.
Overall, CUDs have higher discount percentages than SUDs.
SUDs offer incremental discounts based on how consistently you use certain resources. These discounts apply when you use the resource for more than 25% of the month and can reach up to 30% if the resource runs the entire month. With them, the flexibility is higher but the discounts are lower.
One important thing to note: CUDs will override any usage of SUDs. So if a machine series is eligible to be covered by either a CUD or SUD, the CUD will always be applied first and overwrite the SUD discount. SUDs do not stack with CUDs — it’s one or the other.
Usage patterns
CUDs are beneficial if your usage patterns are regular and predictable. For example, if you’re running a continuous workload, committing to a long-term contract can lead to direct cost savings.
On the other hand, SUDs are perfect for those who have temporary or fluctuating workloads. If you’re using general-purpose VMs for development and testing purposes and usage varies month to month, SUDs automatically adjust to give you discounts based on your actual usage.
Application process
For CUDs to apply, you need to actively purchase them through the Google Cloud Console, which starts your commitment with Google Cloud. Here, you choose between resource-based or spend-based commitments and select the term length. This process requires some upfront planning and understanding of your forecasted resource usage, but offers structured savings.
There’s no manual initiating process for SUDs. As you use resources, Google Cloud automatically applies the relevant discounts based on your usage levels. This automation makes it easier for you to benefit without having to forecast your usage accurately.
Cost management
With CUDs, you can receive higher discounts, which helps with long-term cost control and budgeting. However, if you overcommit and don’t use your committed resources, you will end up paying for unutilized commitments This makes accurate forecasting crucial for CUD purchases.
On the other hand, SUDs offer lower discounts but offer automatic savings and are less risky than CUDs since there’s no usage commitment. Your costs align more closely with actual usage, making them easier to manage if your resource demands are flexible or unpredictable.
Eligibility restrictions
CUDs apply to specific Google Cloud services, such as Compute Engine, Google Kubernetes Engine, and Cloud SQL. They are typically available for VMs, certain machine types, and regions. Resource-based CUDs cover:
- E2 (including shared core)
- N1
- N2
- N2D
- N4
- C3
- C4 (in preview)
- C3D
- T2D
- H3
- C2
- C2D
- M1/M2
- M3
- A2
- G2
- Z3
You can read more about CUD eligibility here.
SUDs are mostly available for long-running VMs. They’re not restricted to specific machine types, making them accessible to a wider range of users. They cover:
- N1
- N1 (shared core)
- N2
- N2D
- C2
- M/M2
You can read more about SUD eligibility here.
CUDs vs. SUDs: Which is right for your business?
CUDs give you higher discounts when you commit to using a certain amount of resources over one or three years. If your business has predictable and stable workloads, CUDs are ideal.
You can use CUDs across many services outside of Compute Engine, such as Cloud SQL, Dataflow, and BigTable. By locking in a commitment, you gain significant savings and budget predictability.
SUDs automatically apply when your VMs run for a significant portion of the month, like with GKE and Compute Engine. There’s no need to opt in, making SUDs convenient for dynamic or changing workloads.
However, SUDs only cover a limited set of machine series and might not be available under special contract pricing, such as Flex Agreements. They also can’t be used for services like App Engine, where spend-based CUDs would be your only discount option.
CUDs summary:
- Best for predictable, stable workloads
- Higher discounts
- Can be used with services outside of Compute Engine, such as Cloud SQL, Dataflow, BigTable, etc.
- Ideal for businesses wanting budget predictability
SUDs summary:
- Automatically applied
- No upfront commitment required
- Covers VMs in Compute Engine and GKE
- Limited to specific machine series
Get the most out of your Google Cloud discounts with ProsperOps
The infrastructure costs of Google Cloud can quickly add up if you don’t manage them well. However, manual cloud cost management can be time-consuming and risky, leaving room for error and potentially leading to overspending. This is why an automated FinOps solution like ProsperOps can be beneficial.
ProsperOps works by inheriting your portfolio of Google Cloud discount instruments and automatically blending them, dynamically adjusting to real-time usage changes. Our platform runs 24/7 in the background to optimize your Google Cloud costs. And best of all? We do it with zero interruption to your operations, minimizing friction and eliminating any ongoing effort on your part.
Ready to see how ProsperOps can optimize your Google Cloud costs? Book a demo today
