System Settings : RAID management : Hot swapping hard disks
 
Hot swapping hard disks
If a hard disk on a FortiManager unit fails, it must be replaced. On FortiManager devices that support hardware RAID, the hard disk can be replaced while the unit is still running, also known as hot swapping. On FortiAnalyzer units with software RAID, the device must be shutdown prior to exchanging the hard disk.
FortiManager 1000 series devices and below do not support hot swapping. For more information, see the Replacing Hard Drives Guide.
To identify which hard disk failed, read the relevant log message in the Alert Message Console widget (see “Alert Messages Console widget”).
To hot swap a hard disk on a device that supports hardware RAID, simply remove the faulty hard disk and replace it with a new one.:
 
Electrostatic discharge (ESD) can damage FortiManager equipment. Only perform the procedures described in this document from an ESD workstation. If no such station is available, you can provide some ESD protection by wearing an anti-static wrist or ankle strap and attaching it to an ESD connector or to a metal part of a FortiManager chassis.
When replacing a hard disk, you need to first verify that the new disk has the same size as those supplied by Fortinet and has at least the same capacity as the old one in the FortiManager unit. Installing a smaller hard disk will affect the RAID setup and may cause data loss. Due to possible differences in sector layout between disks, the only way to guarantee that two disks have the same size is to use the same brand and model.
The size provided by the hard drive manufacturer for a given disk model is only an approximation. The exact size is determined by the number of sectors present on the disk.
The FortiManager unit will automatically add the new disk to the current RAID array. The status appears on the console. The page will display a green check mark icon for all disks and the RAID Status area will display the progress of the RAID re-synchronization/rebuild.
 
Once a RAID array is built, adding another disk with the same capacity will not affect the array size until you rebuild the array by restarting the FortiManager unit.