6The WJ-HDE400 is an extension unit for the network disk recorder (WJ-ND400), which is sold separately.Up to 5 extension units can be connected to one network disk recorder.A maximum of 9 hard disks (hereafter HDD) can be installed in an extension unit and operated as a RAID (Redundant Array of InexpensiveDisks) to increase fault tolerance of the system.HDD fault tolerance is high because it is possible to use the RAID function.This product is equipped with the RAID6 mode that can recover image data when two HDDs fail, in addition to the RAID5 mode that can recoverimage data (RAID6 has two sets of error correcting code data). This prevents loss of recorded image data on large volume HDDs.• To use the RAID5 mode you need to connect 3 or more HDDs, the RAID6 mode requires 4 or more HDDs.• Theoretical volume when RAID5 mode enabledTheoretical volume = HDD with smallest capacity in the unit x (number of HDDs in the unit −1)• Theoretical volume when RAID6 mode enabledTheoretical volume = HDD with smallest capacity in the unit x (number of HDDs in the unit −2)• The capacity of the HDDs that are installed may be a few percents smaller.You can install and remove HDDs by opening the front panel of the extension unit.If more than two HDDs are installed, replacement can be done without stopping recording. Instructions are shown on the LCD to reducemisoperations, and make maintaining and replacing HDDs easy.Use the special HDD canister provided to install the HDD.The HDD unit is an HDD that is in the special canister. The HDD units can be easily installed or removed from the HDD bay slots inside the frontcover of the extension unit.* Contact your dealer for information on purchasing and replacing HDDs.This manual describes how to install and connect the extension unit. It also describes how to install and remove HDDs by operating the buttonson the front panel of the network disk recorder.Refer to the manuals provided with the network disk recorder to use the extension unit in a system.PrefaceHDD Fault Tolerance SystemChanging HDDs is EasyAbout these Operating Instructions