I have a Raid5 array in my server and I have added a new drive and set it to grow using mdadm --grow. I've just realised that I forgot to unmount the array before I did this.

I've turned off nfs and samba so no other machines on the network can access the array, and I won't be using the machine until the grow is complete.

This is a non-bootable data array only, with the root partition on another drive, so I see no reason for the operating system (Ubuntu Jaunty) to access the array.

Should I unmount the array as a precaution, during the grow, or would it be better to just leave it alone now it's started?

Adding the new drive with the array mounted is safe. Just leave it to finish its work. I grew my /home array the same way while working on my computer.

Thanks Gary, that's reassuring.