Drive partitioning is the process of dividing a drive into one or more spaces so that you or the system can manage each space separately. These spaces are called partitions. A drive must contain at least one partition to be in use.

Drive Partition Types

Synology NAS formats a drive into three types of partitions:

• System partition: This partition stores the DSM operating system, user settings (e.g., account credentials, network settings, and Control Panel settings), and system logs.¹ By default, the system uses the mirroring capability of RAID 1 and saves an identical set of system partition data onto every drive in a Synology NAS. When the system detects damaged or failed drives in your Synology NAS, it can still use the system data from a healthy drive for system startup. If multiple healthy drives are available for system startup, the drive with the smaller drive number will be used first. For example, if both Drive 1 and Drive 4 are in a healthy status, then Drive 1 will be used for system startup.
• SWAP partition: This partition serves as a temporary memory resource when the RAM fills up and the system needs more memory resources.² By default, the system uses the mirroring capability of RAID 1 and saves an identical set of SWAP partition data onto every drive in a Synology NAS.
• Data partition: This partition consists of storage pools and volumes. All your data and installed packages are stored here.

Drive Partitioning Operations

The following operations create drive partitions:

• Installing the operating system for the first time: The system formats the drive and creates two drive partitions (the system partition and the SWAP partition).^{3, 4}
• Creating a storage pool or adding drives to a storage pool: The system formats the drive and creates three drive partitions (the system partition, the SWAP partition, and the data partition).⁵
• Creating an SSD cache: The system formats the drive and creates one partition (the data partition).