Resized The RAID And the Data Is Safe

The <a href="">last post,</a> I was talking about resizing a component of my existing RAID. I was worried about losing data.

Here's how I did it without data loss.

/dev/md0                   /dev/sdb1        2TB
                                  /dev/sdc1        1TB

I am increasing the size of the partition and it's an important distinction because the order of the steps would be different otherwise. Check the status of the RAID array with:

$cat /proc/mdstat

Put a fail flag on the partition and remove it.
$sudo mdadm /dev/md0 -fail /dev/sdb1 --remove /dev/sdb1

Then we have to use fdisk to handle the physical resizing of the device. fdisk is an interactive application in text mode. So-
$sudo fdisk /dev/sdb1
-h     for help
-p     for primary partition
-d     delete
-n     new partition
if unsure choose the default option.
-q     to quit without saving
-w    to write the changes, now think first before hitting enter here

I used fdisk to create a new partition utilizing the entire 2TB device. I made an additional step here to check the filesystem after I created a new partition. Use fsck to verify the integrity of the ext3/ext4 filesystem. You should make sure to unmount the partition before checking with e2fsck. It will offer to fix errors you have to press consent or y for the process to continue, otherwise, use the -p switch to allow e2fsck to automatically repair the filesystem without human or administrator intervention.

$sudo e2fsck /dev/sdb1

Re-add the partition to the RAID array.
$sudo mdadm -a /dev/md0 /dev/sdb1

I had to wait 2 hours for the RAID to synchronize and then proceed to the next partition or the next step. Check the status of the synchronization with:

$cat /proc/mdstat

Do this steps one partition at a time.

Increase the size of the array with:

$sudo mdadm --grow /dev/md0 -z max  
$sudo mdadm --grow /dev/md0 -z [size]

Increase the size of the ext3/ext4 filesystem with:

$sudo resize2fs /dev/md0 [size]

If the size is not specified, the default is the size of the partition.

Donato Roque@ubuntu-16-04
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