User manual

TeraStation IS Setup Guide 17
Chapter 5
Changing RAID Mode
• RAID 5 array with 4 hard drives (factory default)
Uses 4 hard drives in one array. Parity information for correcting errors is stored, so access speeds are slower than
other RAID modes. Total usable space is the sum of the capacity of 3 drives. If a drive is damaged, you can recover
data on the array by replacing the damaged drive. You cannot recover data if 2 or more drives are damaged.
• RAID 5 array with 3 hard drives
Uses 3 hard drives in one array. Parity information for correcting errors is stored, so access speeds are slower than
other RAID modes. Total usable space is the sum of the capacity of 2 hard drives. The fourth disk may be used as
a hot spare, which replaces a failed drive automatically. If a drive is damaged, you can recover data on the array
by replacing the damaged drive. You cannot recover data if 2 or more drives are damaged.
• RAID 10 array
Uses 4 hard drives in one array. The space you can use is the sum of 2 hard disks' space. Data will be written
speeded and this makes access speed slightly faster. Since same data are written in the 2 hard disks at a same
time, even though one of the paired hard disks (1-2 or 3-4) is damaged, data can be recovered by replacing the
damaged hard disk (if both 1-2 or 3-4 hard disks are damaged, you cannot recover data).
• RAID 1 array
Uses 2 hard drives in a mirrored array. You can create up to 2 RAID 1 arrays. Total usable space on a RAID 1 array
is the capacity of one of the drives. If either drive is damaged, data can be recovered by replacing the damaged
drive. You cannot recover data if both drives are damaged. The other two drives not used in the RAID 1 array
may be used as hot spares which replace failed drives automatically, or as a second RAID 1 array, or as individual
drives. Or, one may be congured as an individual drive and the other as a hot spare.
Note: After replacing a failed drive in any of the above arrays, le transfer speeds will be slower for several
hours while the RAID array is being rebuilt. During this period, the front LED display will show “RAID ARRAYx
Resyncing”.
Out of the box, your TeraStation is congured with all four hard drives in a RAID 5 array. Many other RAID array modes are
available.
Notes:
・ All data on your drive will be deleted if you change the RAID mode. Back up any important data before
changing RAID modes.
・In this document, "Recovery" means restoring the TeraStation back to the state it was in before a drive failure. It
does not refer to reading data from broken hard disks.