4 minute read

I recently upgraded my Synology NAS from a DS 214play that I’ve had for a few years to a DS 1515+, and bought two additional drives to go along with it. I also wanted to do a fresh start of the configuration and metadata, as I had been having some issues with my existing NAS (in addition to the performance issues that drove me to upgrade), so I did not want to just move the existing drives over and add the new ones to the same array.

I set up the 1515+, and started copying files over using SFTP mounts–however, I was getting abysmal speeds, 10-11 MB/s at best. Both pieces of hardware were connected to a gigabit network, neither was doing anything else at the time, but transfers were incredibly slow. Not wanting to wait a few days to transfer 3 TB of data, I set out to find a better way to transfer.

I knew Synology’s “Hybrid RAID” was just a Linux software RAID, which meant I should be able to mount it in the new Synology as well. I started by doing some exploring with mdadm, checking that the array was not degraded for some reason, etc. However, I couldn’t simply assemble it and mount it—under the software RAID is an LVM volume group. I started by dumping some state about the volume groups:

Aha! vgdisplay is telling me what I want to know already: I have a duplicate volume group, and the existing one that was created here (the new NAS’s VG) is taking precedence over the old one. Armed with the UUID there, I can rename the old VG:

Once it’s been renamed, the next step is to activate the VG so that it gets a /dev entry and becomes mountable:

Once we’ve activated it, we can mount it via its /dev entry, and we can see our entire main storage volume there:

Once the volume group was mounted, I could copy files much faster than copying over the network allowed me—100+ MB/s vs. 10-11.

Important notes:

  • None of these operations should cause data loss, but I am not responsible for any data loss that may occur if you follow my instructions!
  • Be careful when copying the UUID for a rename.
  • More complex Synology setups may not work this easily—I did everything assuming you set up a single volume group, all the drives are in the same RAID array, etc.
    • That said, you should be able to use these same tools on more complex setups, just with more care taken to find the right volume groups.
  • I had to reboot to get the drives back into a state where I could erase them and add them to an existing volume.
  • I would suggest not rebooting your Synology with the old drives plugged in—it is likely to pick up the old volume as a new volume and re-shuffle your volumes and shared folders.
  • These instructions should work on anything that supports LVM/mdraid and the filesystem on the drives (ext4 or btrfs).

Good luck!

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