Managing Dynamic Capacity Expansion on Amazon FSx for NetApp ONTAP

Overview

As enterprise data continues to grow, ensuring scalable and reliable storage becomes essential. Organizations using Amazon FSx for NetApp ONTAP benefit from flexible storage management that supports dynamic capacity expansion. This feature enables administrators to resize iSCSI LUNs on the fly and extend Windows partitions without downtime, ensuring that applications, databases, and workloads continue to run seamlessly.

Introduction

As databases and applications grow, storage expansion becomes inevitable. For Windows servers connected to Amazon FSx for NetApp ONTAP, resizing an iSCSI LUN and extending the Windows partition are among the most common maintenance tasks, especially for SQL Server log or data drives.

In this blog, we will walk you through the process of resizing an FSx ONTAP LUN and extending the Windows partition, including commands, example outputs, and best practices.

Purpose

This guide explains how to safely increase the size of an FSx for ONTAP iSCSI LUN and extend the associated Windows drive typically used for SQL Server logs, data, or application storage.
It ensures that the process is safe, online, and reversible (through snapshots).

Scope

Applies to all Windows servers using iSCSI LUNs provisioned from FSx ONTAP volumes, including:

• SQL Server log or data drives
• Application or middleware drives
• Backup LUNs

Prerequisites

Before you begin, ensure you have:

1. SSH access to FSx ONTAP SVM (via vsadmin).
2. Administrator access to the Windows Server connected to the LUN.
3. Enough free space in the hosting ONTAP volume.
4. A recent database backup or ONTAP snapshot.
5. A maintenance/change window for safe execution.

Step-by-Step Procedure

Let’s now go through each step in detail.

Step 1: Connect to FSx ONTAP

Use SSH to connect to your ONTAP SVM management endpoint.

Example:

Output:

Step 2: Verify Current LUN Size

List all LUNs or a specific one to confirm the existing size.

Output:

Or view details of a specific LUN:

Output:

Step 3: Check Volume Capacity

Ensure the hosting volume has sufficient free space to support the expansion.

Output:

Here, 1.2TB of free space is available, enough to increase the LUN.

Step 4: Resize the LUN

Now, resize the LUN to the desired size (for example, 1 TB).

Output:

LUN successfully resized to 1TB.

Step 5: Verify the LUN Resize

Check the updated LUN size.

Output:

You can now see the new size reflected correctly.

Step 6: Rescan Disks in Windows

Once the LUN is resized in ONTAP, refresh Windows to detect the additional space.

Option A: GUI (Disk Management)

1. Open Disk Management (msc).
2. Click Action → Rescan Disks.
3. Wait for Windows to recognize the new unallocated space.

Option B: PowerShell Command

You can also do this via PowerShell:

Output:

Step 7: Extend the Windows Partition

Once the OS detects the additional space, extend the drive:

1. Open Disk Management.
2. Locate the LUN (e.g., SQL-Log (L:)).
3. Right-click and select Extend Volume.
4. Follow the wizard → select the unallocated space → click Next → Finish.
5. Confirm the new size is reflected.

Before Resize:

After Resize:

Drive successfully extended to 1TB.

Optional PowerShell Verification

Check the updated size using PowerShell:

Output:

Risks and Mitigation

Note:

• No downtime is expected, ONTAP LUN resize is an online operation.
• Data loss is not possible since resizing only adds capacity.
• Still, perform the maintenance during a scheduled window for safety.

Rollback Plan

If something goes wrong after resizing:

1. SQL workloads will continue running on existing data since resizing is additive.
2. ONTAP Snapshot Restore:
   You can revert to the last snapshot if any data issue is found.

3. Database Backup:
Restore from your latest SQL backup if snapshots are unavailable.

Note: Shrinking a LUN is not supported. The only rollback option is to restore from a snapshot or backup.

Best Practices

To ensure a reliable and safe LUN management process:

• Monitor volume utilization regularly using ONTAP CLI or AWS Console.
• Always take a snapshot before resizing.
• Avoid over-allocating unused storage.
• Document every resize activity, including the date, old size, new size, and reason.
• Use CloudWatch metrics to set alerts for FSx volume capacity thresholds.

Conclusion

Resizing an FSx for ONTAP LUN and extending a Windows partition are straightforward and risk-free operations when done carefully.
With the right steps, including verifying volume capacity, resizing the LUN, rescanning disks, and extending the partition, you can easily scale your storage on the fly.

Drop a query if you have any questions regarding Amazon Fsx and we will get back to you quickly.

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