Assemble a Storage Pool

This article guides you through how to assemble an Available Pool or a crashed or missing storage pool.

Assemble an Available Pool

In the past, your Synology NAS must be restarted if you want to assemble a storage pool previously created on another Synology NAS. To save the hassle of system restart, Synology developed Online Assemble -- a mechanism for assembling and converting a storage pool back to the available status without restarting your system.

Once the drives previously installed in another Synology NAS have been switched to your current Synology NAS, the system will detect the drives and scan the relevant data (e.g., RAID type and SSD cache), checking whether the drives installed in the current Synology NAS meet the criteria for assembling the storage pool previously created on another Synology NAS.

Criteria required for Online Assemble:

You can perform Online Assemble to assemble a storage pool when all the following criteria are met:

The drives currently installed in your Synology NAS were previously used for storage pool creation on another Synology NAS.
The drives currently installed in your Synology NAS are not initialized.
The number of drives currently installed in your Synology NAS is sufficient for assembling an Available Pool.

The Available Pool information will be triggered and appear in the Storage page when the aforementioned criteria are met.

Conditions that will not trigger Available Pool:

Please note that the Available Pool information will not appear if the installed drives meet any of the following conditions:

The number of the installed drives is smaller than the minimum number of drives required for the storage pool in a certain RAID configuration.
For example: For a RAID 5 storage pool created by four drives and tolerable of one drive failure, the Available Pool information will not appear when less than three drives are installed in the current Synology NAS.
One or multiple SSD read-write caches are missing because the number of the installed drives is insufficient.
For example: For a storage pool on which an SSD read-write cache and an SSD read-only cache has been created on Volume 1 and Volume 2 respectively, the Available Pool information will not appear when the SSD read-write cache is missing.

Note:

If you did not click the Online Assemble button to assemble an Available Pool, the Available Pool information indicating that the storage pool can be assembled online will still retain after the system restarts.
A storage pool previously created on a Unified Controller cannot be assembled on a Synology NAS.

To assemble an Available Pool:

If the Available Pool information appears in the Storage page, please follow the steps below to assemble the Available Pool:

Go to the Storage page and click on Available Pool to expand its information.
Click the Online Assemble link or click the upper-right icon and select Online Assemble.
Confirm the settings and click Start.
Once the assembling is successful, the name Available Pool will automatically change to Storage Pool, while the storage pool information remains the same.

Note:

If the assembling fails, the status of the Available Pool will change to Assemble failed and the Online Assemble button will not be clickable. If this situation occurs, we recommend restarting your system to assemble the Available Pool.

To remove an Available Pool:

Please do the following if you do not want to assemble an Available Pool and want to remove it:

Go to the Storage page and click on the Available Pool you want to remove.
Click the upper-right icon and select Remove.
Read the message carefully and click Remove.
Confirm that you want to remove the Available Pool and click Delete.
Enter the password of your DSM account and click Submit.

Note:

All data on all drives of the Available Pool will be erased once the Available Pool is removed. Please make sure you have backed up important data before proceeding.

Assemble a Crashed or Missing Storage Pool

If a storage pool is in Crashed or Missing status, it means that the detected storage pool cannot be successfully assembled either because the number of installed drives is insufficient or a drive has been mistakenly removed from Synology NAS while the system is still powered on.

Crashed: This status indicates that the number of installed drives is insufficient for assembling the detected storage pool, or a drive has been mistakenly removed from your Synology NAS while the system is still powered on.
Missing: This status indicates that no drives can be detected.

A storage pool in Crashed or Missing status can still be assembled through Online Assemble once the following criteria are met:

A sufficient number of drives has been installed for assembling the storage pool.
The serial number of the detected drives must be identical to the serial number of the drives shown in Required Drive Info.

Once the aforementioned criteria have been met, the Crashed or Missing status will change to Can be assembled because drives are detected. Once you see this status, please follow the steps below to assemble the storage pool:

Click the Online Assemble link or click the upper-right icon and select Online Assemble.
Confirm the settings and click Start.

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