How can I resize a SoftRAID volume?

SoftRAID does not support adding disks to an existing volume to increase its capacity. For example, you cannot start with a 3-disk RAID 5 and add a fourth disk to grow it. (The only exception is mirror volumes, where additional disks can be added.)

However, you can expand your volume by replacing each existing disk with a larger one — without losing your data.

Example: You have a ThunderBay with four 12TB drives in a RAID 5 volume (36TB usable). You replace each drive one at a time with 18TB drives. Once all four drives have been replaced and the volume has rebuilt after each swap, SoftRAID will allow you to expand the volume up to 54TB.

Before You Begin

Back up your data. Always maintain a current backup before making any changes to your storage. This process requires removing drives from a live RAID volume one at a time, and while SoftRAID is designed to handle this safely, no storage operation is without risk.

Step 1: Certify Your New Drives

We strongly recommend certifying all new drives before putting them into service. Drives receive only minimal testing at the factory — certification is the only way to verify that every sector on the drive can reliably store data before you trust it with your files.

SoftRAID’s 3-pass certify writes random data to every sector, reads it back, then writes zeros — leaving the drive in “as new” condition. Any drive that fails certification has a confirmed problem and should be returned before it ever touches your RAID.

Time estimates:

• HDDs: approximately 1 day per 2TB of capacity. A 24TB drive will take about 12 days to certify.
• SSDs/NVMe: a 2TB SSD typically takes 4–8 hours for a 3-pass certify.

Tip: You can certify all your new drives at the same time to save time overall. Connect them all to your enclosure (using available empty bays, a second enclosure, or a dock) and start certification on each one before you begin the swap process.

To certify: select the disk tile → Disk menu → Certify Disk.

Step 2: Replace the First Drive

• Identify the first drive to replace. Use Disk menu → Blink Disk Light to confirm which physical drive corresponds to which disk tile in SoftRAID. Alternatively, you can simply start with Tray A and work across in order — replacing B, then C, and so on.
• Unmount the volume, wait for activity lights to stop, then remove the drive from its bay.
• Insert the new (certified) drive into the same bay.
• Open SoftRAID — the new drive should appear in the disk list within a few seconds.
• Initialize the new drive: select its disk tile → Disk menu → Initialize.
• Select the volume tile → Volume menu → Add Disk → select the new drive.
• SoftRAID will begin rebuilding the volume automatically.

You can continue using the volume while the rebuild is in progress, though performance may be reduced.

Step 3: Wait for the Rebuild to Complete

Do not remove another drive until the rebuild is fully complete. Removing a second drive from a RAID 5 volume while a rebuild is in progress will result in data loss.

Monitor rebuild progress in the volume tile — you will see an I/O counter and a time remaining indicator. Rebuild speed depends on your Volume Optimization setting:

• Workstation — rebuilds at approximately 50% speed; you can continue working normally (recommended)
• Server — rebuilds at 100% speed; volume performance will be reduced during rebuild
• Digital Video / Photography / Digital Audio — pauses rebuilding during active use; resumes at full speed when idle

To change the optimization setting at any time: select the volume tile → Volume menu → Optimize for.

Step 4: Repeat for Each Remaining Drive

Repeat Steps 2 and 3 for each drive in the enclosure, one at a time. Always wait for the rebuild to complete before removing the next drive.

Step 5: Resize the Volume

Once all drives have been replaced and the final rebuild is complete, SoftRAID will allow you to expand the volume to take advantage of the additional capacity.

• Unmount the volume.
• Select the volume tile → Volume menu → Disable Safeguard (you will need your administrator password).
• Select the volume tile → Volume menu → Resize Volume.
• To use the maximum available space, leave the setting at Max. If you want a specific size (for example, to leave room for a second volume), enter your desired capacity.
• Click Resize. This step completes in seconds.
• Re-enable Safeguard: Volume menu → Safeguard → Enable.

Important Notes

HFS+ volumes have a resize limit. When you resize an HFS+ volume, the allocation block size remains fixed from the time the volume was originally formatted. This means there is a limit to how much larger the volume can grow without reformatting. The exact limit depends on the original volume size and block size, so results may vary.

APFS volumes have no such limitation. APFS volumes can be resized indefinitely as capacity grows.

Only the most recently created volume on a set of disks can be resized. If you have multiple volumes on the same disks, only the last one created is eligible for resizing.