XPenology Raid Expansion

Expand the volume if Synolgy DSM doesn’t want to

While running XPEnology, my virtual Synology DS3615xs Disk Station, I came across an odd problem preventing me from expanding my volume after adding more disks. Whatever I did, the DSM volume did not want to expand beyond a certain size, but this is how I solved the problem.


I’m not responsible if you screw up by following these steps.
Always do a complete backup before making any changes to the file system.

Why does my volume not expand?

Even after extensive debugging, I’m not sure why DSM doesn’t want to expand the volume. The only thing I can confirm is that there is no 16TB limit, even though I thought so in the beginning. The log files either show that you are out of reserved GDT blocks or that the volume has expanded successfully even though it didn’t. DSM is basically just using LVM and mdadm so it’s not a problem to expand it manually.

How to expand your volume

These guidelines are tested with SHR2 and a single volume only! SHR should be fine too, but normal raid-setups do not use lvm as far as I know. Even thought the concept would be the same, the commands would most likely differ (instead of expanding though lvm you would probably just use mdadm). Anyway….

Follow these steps:

1. The first step is to download Ubuntu Desktop 64-bits and either burn it onto a CD or make a bootable USB-drive. Then insert and boot it on the machine running Synology DSM. Remember to select “Try without installing” so you don’t write any data to the disks.

2. First we need to install mdadm since it’s not included by default. Just accept the default values as they don’t matter in this case:

sudo apt-get install mdadm

3. We need to assemble the raid.

sudo mdadm --assemble --scan

4. Run the following commands, line by line. This will load the necessary module, scan for lvm volumes and activate the volume:

sudo modprobe dm-mod
sudo vgscan
sudo vgchange -ay vg1000
sudo lvs

5. Run a file system check. This may take some time:

sudo fsck.ext4 -fvp /dev/vg1000/lv

6. Expand the volume. This may take a while! You may open a new terminal window and use “top” in order to see what’s going on:

sudo resize2fs -fpF /dev/vg1000/lv

7. Just reboot the system, remove the CD and boot into DSM. It should be all green, no crashed volume!

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