LG N4B2N User Manual page 191

Appendix A Volume Construction & RAID
Configuration
• RAID5 Parity volume
The Disks are configured in parallel so as to all be used at once to store data;
parity (P) suggests that when the Disk is damaged the system will not be affected,
which is the system that the volume uses. At least 3 Disks are needed as well
as parity save capacity of 1 Disk, thus 1 Disk can be damaged without system
malfunction.
Data backup and the safeguarding of saving capacity occur simultaneously, where
the volume capacity is equal to the minimum Disk capacity multiplied by the number
of Disks in the volume minus 1. Due to parity calculation, data saving is retarded.
Data backup and the safeguarding of saving capacity occur simultaneously.
- If one Disk is damaged in RAID5, the state of the volume is indicated as "Faulty".
The Disk that backs up data must immediately be changed in the event of its
malfunction. If more Disks are damaged, data will be permanently lost. Thus the
Disks must be exchanged with either the server off or left on (hot swapping). After
the Disk is replaced, the volume will be in a "syncing" state. After the backup is
finished, the system will be in a normal "active" state.
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