Microsoft 365 Storage Optimization: Costs, Quotas, and Digital Sustainability

In the Microsoft 365 ecosystem, storage is the silent engine of productivity. It ensures access to information through SharePoint, OneDrive, and Teams. However, with exponential data growth, storage capacity is no longer an unlimited commodity.

For large enterprises, volumes now reach several petabytes (1 PB = 1,000 TB). The stakes are becoming critical: financial drift (overage costs), environmental impact, and governance (compliance, security).

This management, whether driven by a responsible digital approach (CSR) or budgetary rationalization, is essential to prevent spaces from being saturated with obsolete data.

In this article, we detail the storage management mechanisms in Microsoft 365, the actual costs, and methods for engaging users.

In the Microsoft 365 environment, it's essential to distinguish individual storage from collaborative storage.

OneDrive for Business: Individual Space

OneDrive is designed for personal work documents before sharing.

• Standard quota: 1 TB per user by default for most subscriptions.
• Possible extension: For eligible plans (e.g., E3, E5) and if the user reaches 90% of their space, the administrator can increase this quota up to 5 TB. Beyond that, a specific request to Microsoft support can unlock up to 25 TB per user.

Monitoring is done through 4 storage states (Under Limit, Nearly Full, Full, Exceeded). Quota management now operates primarily through the Microsoft 365 Admin Center (Users section) or via PowerShell for bulk modifications.

SharePoint Online: Collaborative Spaces

SharePoint storage (team sites, libraries, Teams) draws from the tenant's global quota described above.

• Technical limit per site: A single site can host up to 25 TB of data.
• Warning: While this technical limit is high, it is often greater than the global quota of many SMBs. Therefore, it is risky to leave sites in "automatic management" without monitoring.

Administrators can set storage quotas per site (manual) to prevent a single project from consuming the entire company's capacity.

Purchasing additional storage should only be a last resort. Here's how to optimize what you have:

Monitor Inactive Resources

Use Microsoft 365 usage reports to identify SharePoint sites and Teams workspaces with no activity for 90 or 180 days. Deleting or archiving these containers is the quickest lever for reclaiming space (and reducing the attack surface).

2. Industrialize Storage Limits (Quotas)

Don't leave sites in "Automatic" mode. Apply a default limit (e.g., 100 GB per project site) during creation. This forces owners to request a justified extension rather than storing unnecessary data.

3. Leverage Microsoft Purview for Lifecycle Management (DLM)

Don't just store—manage end-of-life:

• Retention labels: Configure rules to automatically delete obsolete data after a given period (e.g., 5 years for accounting documents, 1 year for temporary files).
• Teams & Exchange: Enable retention policies to automatically clean up old conversations and logs that no longer have business value.

4. Master Versioning

Microsoft recommends configuring versioning in "automatic" mode, so the system intelligently optimizes storage by progressively retaining fewer old versions. In "manual" mode, SharePoint can keep a maximum of 500 major versions of a document. For large files (PPTX, videos), this exponentially multiplies the space occupied.

5. SharePoint Advanced Management: Your Ally for Storage Cleanup

SharePoint Advanced Management (SAM) is included in SharePoint Premium. Microsoft designed it to help you manage your storage efficiently.

Here's what it does for you:

• Identifies abandoned sites: It detects SharePoint sites and Teams that no one uses anymore
• Identifies risky shares: It scans permissions and shows you which content is accessible to too many people
• Prepares your data for Copilot: It cleans up your data sources so Copilot gives you more accurate answers

💡 Don't have SAM? Use Microsoft 365 usage reports combined with PowerShell scripts. You can generate lists of large files, duplicates, or documents not accessed in months.

Your Users Are the Key: Raise Awareness About Responsible Storage

You can deploy all the tools in the world, but your employees create 80% of the data. You need to make them understand that the cloud has physical limits and an environmental cost.

Microsoft Sustainability Manager allows you to visualize the carbon footprint of your cloud infrastructure, including Microsoft 365 storage.

The message to convey: Even if you don't access the sustainability dashboard, every GB deleted reduces the company's CO2 emissions (Scope 3).

(Note: This tool requires specific licenses. Not all M365 offerings provide access. Check your eligibility with your Microsoft partner).

5 Simple Actions to Promote Among Your Teams

Suggest these habits to your colleagues:

• Empty the SharePoint and OneDrive recycle bin each month
• Clean the "Downloads" folder (local and cloud)
• Delete draft versions once the document is finalized
• Share links instead of sending large attachments
• Archive completed projects instead of leaving them active

You thus transform storage management into a double win: you control your costs and you strengthen your CSR approach.

While native tools (Admin Center, Purview) are powerful for IT administrators, they often leave end users in the dark.

The MyDataManagement solution by IDECSI bridges this gap by giving each employee and data owner immediate visibility into their digital footprint.

Beyond simple reporting, the solution enables users to:

• Visualize large, obsolete, or unused spaces.
• Act directly through a simplified interface to archive, delete, or review access.
• Empower business units by giving them the means to contribute to the company's governance and sustainability strategy.

As a complement to Microsoft 365 usage reports, MyDataManagement makes storage maintenance distributed and continuous, thus avoiding costly emergency cleanup campaigns.