How to replace a drive in Synology NAS

Dead drive? Here’s what to do.

Drives do not last forever, including those specifically designed for network-attached storage (NAS). If you somehow come across a dead drive inside your Synology NAS, there are some things you should consider and steps to take to replace it without losing data.

What you should know before replacing a drive

Synology has a Replace Drive feature in DiskStation Manager, which facilitates the process of replacing drives, be it a dead one or a drive with lesser capacity. This is what we’ll be using for this guide.

Synology also has a handy RAID calculator that can also provide insight into whether replacing a drive will affect the current capacity of the storage pool. The “Replace Drive” button will only be available to NAS with a configured SHR, SHR-2, RAID 1, RAID 5, RAID 6, RAID 10, or RAID F1.

The storage pool also needs to be composed of at least two drives and the Synology NAS needs to contain at least one drive that’s not in use. Only a single drive can be replaced at any given time and SATA/SAS, HDD/SSD drives are not interchangeable. As always, I recommend you back up your data!

How to replace a drive in Synology NAS

If you’ve got a damaged or dead drive inside the Synology NAS, it’s easy to swap it out for a new one. Note: this process will clear the replacement drive, so ensure it’s empty and/or you’ve backed everything up.

If you have a spare drive bay

When you’ve got spare bays available, the process is incredibly straightforward:

  1. Log into your Synology NAS.
  2. Go to Storage Manager > Storage.
  3. Click on the three-dot icon on the storage pool that includes the drive you wish to replace.
  4. Select Replace Drive.
Synology DSM 7 Storage Manager
Synology DSM 7 Storage Manager

Should the Synology NAS determine the unused drives cannot serve as replacements, a message box should appear informing you of the reason.

  1. Select the drive you want to remove from the storage pool.
  2. Click Next.
  3. Select the drive you want to add to the storage pool.
  4. Click Next.
  5. Click OK.
  6. Click Apply.

The Synology NAS will now activate the replacement process, which will be reflected in the storage pool status. Once complete, the original drive will be deactivated and ready for removal.

If your NAS is full of drives

If you do not have space to install a clean drive without removing one already attached to a storage pool, follow these steps:

  1. Log into your Synology NAS.
  2. Open Storage Manager.
Synology DSM 7 Storage Manager
Synology DSM 7 Storage Manager
  1. Click on HDD/SSD.
  2. Note the number of the drive that you wish to replace (or the one with a detected fault).
  3. Look at your Synology NAS and count from the left.
  4. Remove the drive tray from the NAS. (Power down the enclosure if it doesn’t support hot-swapping.)
  5. Replace the drive with the new one on the tray.
  6. Install the new drive by reinserting the drive tray.
  7. Open Storage Manager.
  8. Click on the affected volume on the left sidebar.
  9. Click on Manage.
  10. Click on Repair.
  11. Follow the wizard.

How to expand storage pool in Synology NAS

Choosing the best NAS drives for your Synology enclosure ensures you will have ample capacity to store all your data on reliable mediums. It’s inevitable that you’ll eventually run out of space if more data is transferred to the NAS. This is when we should expand the storage pool by adding larger drives.

It’s important to ensure your storage pool is in a “Healthy” state before progressing with increasing the amount of space in the storage pool.

How it’s recommended to go about expanding the storage pool in Synology NAS depends on the RAID type employed.


If using Synology Hybrid RAID, you need to bear in mind the following:

  • If all your drives are the same capacity, you’ll need to replace at least two larger drives to expand the storage pool with SHR. (If you have three 2TB drives, you’ll need to replace two of them with larger drives.)
  • If your installed drives are of different capacities, the new drives must be larger than the largest drive installed. (If you have 1TB, 2TB, and 4TB drives installed, the new drive(s) will need to be at least 6TB.)

RAID 1, RAID 5, RAID 6, RAID 10, and RAID F1

Should you be using RAID 1, RAID 5, RAID 6, RAID 10, or RAID F1, you’ll want to follow the following guides in replacing a drive (or few) to expand the storage pool:

  • RAID 1: (smallest drive size)
  • RAID 5: (number of drives – 1) x (smallest drive size)
  • RAID 6: (number of drives – 2) x (smallest drive size)
  • RAID 10: (number of drives / 2) x (smallest drive size)
  • RAID F1: (number of drives – 1) x (smallest drive size)
Seagate IronWolf

Seagate IronWolf

I’m a big fan of Seagate’s IronWolf series of NAS hard drives. If you’re serious about storage, the Pro range offers a few advanced extras.

Western Digital SA500
Western Digital SA500 (Source: Western Digital)

Western Digital Red SA500

There’s plenty to love about the Western Digital Red SA500. There’s a good warranty, excellent endurance rating, and brilliant data speeds.

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