Cannot Add Drive to RAID 5

[MOTU83]

Hello,

I am trying to add a disk to my existing RAID5 but when I go to management, the option to add disk is greyed out.

All disks are 3TB.

I recently migrated from RAID1 with two disks to RAID5 with 3 with no issues.

Is there something else I need to be doing before I can add the disk?

Thank you,
Richard

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[orion]

I'm guessing that your disk-4 might be slightly smaller than the other disks, although it shows 2.73GB. You can check the total sector count on each disk if you know how to use ssh.

[MOTU83]

Thanks, I will try and have a look tonight.