Synology Volume Backup - Passing the 16 TB Volume Limit
I have a NAS (Network Attached Storage), which many people enjoy for backing up content and accessing it in one place on their network. I bought one back in 2018 or so with only two drive slots. I put in two 4 TB drives, and it was great for the time. If one drive died, I could replace it rather quickly.
Fast forward to 2024, and I bought a DS1821+ with eight drive slots. I filled up five slots with 8 TB drives. According to the Synology RAID Calculator, I was supposed to be getting 21.8 TB, even with SHR-2. I was only getting 16TB.
So what gives? As it turns out, because my drive was created on a 218j the max volume size was 16TB. This carried over to the new DS1821+. When I realized this, I had 6 TB of stuff.
Fixing the Problem
So I put another 8TB drive in the last slot and created a storage pool and volume with it. The steps was as follows.
- Create a new storage pool and volume (Volume #2)
- Back up all data from the first storage pool into the new volume (Volume #1 into Volume #2)
- Erase volume #1 and recreate the storage pool
- Transfer data from Volume #2 back to Volume #1.
To get all my data from Storage Pool #1 to #2, I SSH'd into my NAS and ran the following command on a spare computer I could leave on. I could have done it with a scheduled task on the NAS, but I wanted to view the progress in real time throughout the day and ensure it was still going.
sudo rsync -auhv --info=progress2 /volume1/ /volume2/backup
This process took about a day for 6TB of stuff. I then erased Storage Pool #1 and recreated it. Again, this process took a day to recreate the raid. I noticed I now had 21 TB!
I then ran the following command via SSH, essentially the first one in reverse. This moved faster as the write speed was better across the 5 drive Volume rather than writing to one drive.
sudo rsync -auhv --info=progress2 /volume2/backup /volume1/backup
The reason I made a new folder called "backup" is because I need to recreate the shares and manually move over the data via SSH once the shares were created. I didn't want any folder name collision shenanigans.
Permissions Pitfall
Apparently, when I ran the rsync command to run the data back to Storage Pool #1, the permissions were screwed up. I had to run chmod on the directory to get it to allow me into the new share, regardless of what the Synology UI said the permissions were.
sudo chmod -R 755 backup
And that fixed that issue.