QNAP Security VioStor NVR (Version: 3.3.2) - Manual (Page 144)

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 Configure spare drive
This function enables adding or removing a spare drive from a RAID 5 configuration.
The options available are:
- Add a spare drive to a RAID 5 configuration
- Remove a spare drive from a RAID 5 configuration
For detailed operation instructions, click ‘Comment’ on the management interface.