I have created a raid5 array with 4 disks. Initially i had 3x 3tb and 1x 4tb (because 3tb was unavailable at the time). After some years i have replaced most of these disks and have come to the point where all array disks are now 4tb in size. Still my mdadm array is 3TB. Is there any way to change the mdadm array size to match the 4tb disk size w/o loosing my data? Thanks for your help!

1 Answer 1


If you have a write-intent bitmap, remove it

mdadm --grow /dev/mdX --bitmap none

Then grow the array

 mdadm --grow /dev/mdX --size max

Finally, restore the bitmap if you were using one

 mdadm --wait /dev/mdX
 mdadm --grow /dev/mdX --bitmap internal

This is all from the RAID Wiki

Things are different if your RAID is on partitions rather than full disks, as you'll have to remove, resize, and then re-add each disk in turn. Wait for a full resync after each disk partition has been extended

Finally you'll need to grow the filesystem or PV that site on top of your RAID. (You can do this any time after the second step.)

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