Linstation 220 - unable to rebuild array

[PoBear]

One of the dives in my linkstation 220 has failed. I've replaced it with the recommended WD Red Pro 4TB disk. I've formatted the new drive and i is 2Gb smaller than the surviving drive so I can't rebuild the array

Any way around this as I haven't 4Tb free on my other drives to copy the data of the array so I format both disks?

[1000001101000]

That's frustrating.

hypothetically you could:
create a new raid1 array on the new drive (now you'd have two raid 1 arrays each with only one drive)
format that array and mount it somewhere
copy all your data from the old array to the new array.
try booting with just the new drive and ensure all your data is accessible as expected.
wipe the old drive and add it to the new array.

I say hypothetically because you'd need to do this from the command line and I'm not entirely sure how ensure that the stock firmware will recognize your new array. What you should really do is backup the whole thing then recreate the array with both drives and copy everything back.

As the top of the page reminds us: "RAID is not a replacement for a backup!".

[PoBear]

Yes, it looks like that is my only option, this failure is turning out to be very expensive as I am going to have to by another drive for the copy.