How to expand a NAS drive – and how it effects your existing RAID

NAS Drive Expansion

I have some questions relating to drive expansion on SHR/BTrFS, QTS/Ext4 and QTS-hero/ZFS. On each of these combinations, …

(1) Can you begin with 1 drive without being locked into JBOD, RAID 0, RAID 1 or RAID 5?
(2) Can you begin with RAID 1, and later, easily change/expand to RAID 5?
(3) Can four drives set up as two RAID 1 pairs be easily expanded to a 4-drive RAID 5?
(4) I know that SHR/BTrFS allows expansion with larger drives without loosing their capacity. Can either of the others do this?
(5) In each of the combinations, if an additional drive is added to a RAID 5, can the data be evenly distributed over the whole RAID? …easily?

On all systems you can start with a single drive, or any number of drives and expand your chosen RAID later.

You can start with a RAID1 and migrate to different RAID later. Only exclusion is RAID0.

You can set up two RAID1 pairs, but you can not merge them into a different RAID. You change each of these two RAIDs into something else though.

Only SHR allow you to mix drives with different capacities. Other RAID types will see bigger drives as big as the smallest drive in the RAID.

If you add another drive to a RAID5 or any other RAID, data will be re-written evenly across the all drives. This is how RAID works in order to make redundancy work.


To change the RAID type of a storage pool on Synology:

  1. Open Storage Manager.
  2. Go to Storage Pool.
  3. Select the storage pool you wish to change and click Change RAID Type from the Action drop-down menu.
  4. Select the RAID type to which you want to change the storage pool. Click Next.
  5. Select which drive to add to the existing storage pool. Then click Next.
  6. Follow the instructions of the wizard to finish. Please note existing data on the added drive shall be deleted.





Changing the RAID Type of a RAID Group on Qnap

You can change the RAID type of an existing RAID group online, without losing access to data or any interruption to NAS services. Changing the RAID type of a RAID group is called RAID migration. QTS allows the following migrations:

Original RAID Type

New RAID Type

Extra Disks Required






One or more



One or more


Migration from a single disk to RAID 6 is performed in stages. First migrate the group to RAID 1, then to RAID 5, and then finally to RAID 6.

  1. Go to Main Menu > Storage & Snapshots > Storage/Snapshot.
  2. Verify the following:
    • The NAS contains one or more available disks.

    • The capacity of each available disk is equal to or greater than the smallest disk in the RAID group.

  3. Select a storage pool or single static volume.
  4. Click Manage.
  5. Select a RAID group.
  6. Select Manage > Migrate.
  7. Select one or more disks.
  8. Click Apply.

    All data on the selected disks will be deleted.

    A confirmation message appears.

  9. Click OK.

    The RAID group status changes to Migrating.

The RAID type changes and then the RAID group status changes back to Ready when migration is completed.

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