Chapter 3 Changing Raid Mode; What Is Raid; Overview; Notes - Buffalo HD-H Series User Manual

Chapter 3 Changing RAID Mode

What Is RAID?

Overview

RAID is a system of combining multiple hard drives for use as a single hard drive, increasing hard drive speed, and
enabling easy recovery in the event of hard drive failure.
Note: If you change the RAID mode, all data on the array is deleted. Always back up any important data before
performing actions that affect your RAID array.
Details of each RAID mode are described below:
RAID 6 (Default Settings)
Combines 4 or more drives into a single array. RAID 6 writes data with parity so that the access speed is slower than
RAID 0 array. The usable space is equal to the sum of the capacity of all drives minus the capacity of two drives. If 2
drives in the array are damaged, you can recover data by replacing them. If 3 or more drives are damaged, your data
is lost.
RAID 5
Combines 3 or more drives into a single array. RAID 6 writes data with parity so that the access speed is slower than
RAID 0 array. The usable space is equal to the sum of the capacity of the hard drives minus the capacity of one drive.
If one drive in the array is damaged, you can recover data by replacing the damaged drive. If 2 or more drives are
damaged, your data is lost.
RAID 0
Combines 2 or more hard drives into a single array. The usable disk space is the total space of all drives used. This
simple RAID mode offers faster performance than RAID modes that include parity. If a single drive in the array fails,
then all data in the array is lost.

Notes

• Whenever a RAID array is built, all data stored on the unit is lost. Be sure to back up your data before building the
RAID array.
• Even if the RAID array is created for redundancy, this will not avoid data loss by accidental erasure or software
fault. Backing up regularly is recommended.
• Even if the RAID array is created for redundancy, the data will be lost when multiple hard drives fail at the same
time. When a drive fails, replace the defective drive to a new one immediately.

Working with RAID Arrays

Follow the procedure below to build a RAID array.
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