This article provides information on how you can expand the capacity of a storage pool or volume.

Before proceeding, use the RAID calculator to estimate the capacity after expansion according to your storage configuration.¹

Adding drives

If your Synology NAS contains empty drive slots, you can install additional drives and add them to an existing storage pool for capacity expansion. For detailed instructions, refer to the help articles for DSM 7 and DSM 6.2.

Only the following RAID types allow for storage expansion through drive addition:

• JBOD
• RAID 5
• RAID 6
• RAID F1
• SHR-1 (with 1-disk redundancy) consisting of at least two drives
• SHR-2 (with 2-disk redundancy) consisting of at least four drives

Replacing with larger drives

To replace drives with ones of a larger size, refer to the help articles for  DSM 7 and DSM 6.2. Note that drive replacement is unavailable for storage pools consisting of only one drive.

Only the following RAID types allow for storage expansion through drive replacement:

• RAID 1, RAID 5, RAID 6, RAID 10, and RAID F1
  • If all drives in the storage pool are of the same size, replace all drives one by one with larger ones.
  • If the drive sizes vary, replace the smallest drives with larger ones to maximize drive usage.
• SHR-1 (with 1-disk redundancy) and SHR-2 (with 2-disk redundancy)
  • If all drives in the storage pool are of the same size, replace at least two drives for SHR-1 (four for SHR-2) one by one with larger ones.
  • If the drive sizes vary, replace the smallest drives with drives that are equal to or larger than the largest drive in the storage pool.

Change RAID Type with drives

You can install additional drives and use them to change the RAID type of an existing storage pool for capacity expansion as long as there are empty drive slots in your Synology NAS. For detailed instructions, refer to the respective help articles for DSM 7 and DSM 6.2.

Only the following RAID type changes allow for storage expansion:

• Basic to RAID 5
• RAID 1 to RAID 5
• RAID 5 to RAID 6 with 2 or more drives
• SHR-1 to SHR-2 with 2 or more drives

Other methods

If the RAID type of your storage pool does not support storage expansion, you may consider the following methods:

• Pair your Synology NAS with one or more expansion units for additional storage capacity.²
• Migrate the system and data on your Synology NAS to a Synology NAS model with more drive bays, and then add drives to create more storage pools or volumes.
• Create another storage pool and volume. You can create them with the available drives in your Synology NAS or by adding drives. For detailed steps, refer to the respective help articles:
  • Create a storage pool (DSM 7 and DSM 6.2).
  • Create a volume (DSM 7 and DSM 6.2).
• Reset the system and restore all the backed-up data to a new storage pool created with drives of a larger size.
  1. Back up all of your data.
  2. Power off your Synology NAS and then replace all the drives with ones of a larger size.
  3. Power on your Synology NAS and then reinstall DSM.
  4. Create a new storage pool and volume.
  5. Restore the backed-up data to the new storage pool and volume.