Changing Raid Modes - Buffalo TeraStation III iSCSI TS-IXL User Manual

Chapter 5

Changing RAID Modes

By default your TeraStation unit is configured with all four hard drives in a RAID 5 array, with other RAID array modes
available for configuration.
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, the term "Recovery" means reverting the TeraStation back to the state prior to the RAID mode
change. It does not refer to reading data from failed hard drives.
• RAID 5 mode (4 hard drives) (factory default)
Arranges 4 hard drives in one array. Parity is stored (to reconstruct data in the case of an error), so total usable space is the
sum of the capacity of 3 drives, and access speeds will be slower than other available RAID modes. If one of the drives fails,
you can recover data on the array by replacing the damaged drive. However, data cannot be recovered if 2 or more drives
become damaged.
• RAID 5 mode (3 hard drives)
Arranges 3 hard drives in one array. Parity is stored (to reconstruct data in the case of an error), so total usable space is the
sum of the capacity of 2 drives, and access speeds will be slower than other available RAID modes. The fourth drive may be
configured as a hot spare that will automatically replace a failed drive. If one of the drives fails, you can recover data on the
array by replacing the damaged drive. However, data cannot be recovered if 2 or more drives become damaged.
• RAID 10 mode
Arranges 4 hard drives in one array, with 2 stripes of mirrored drives. Total usable space is the sum of the capacity of 2
hard drives. Data will be written speeded, increasing access speed. Since data is written into 2 hard drives at the same
time, even if one of the drives fails, data can still be recovered by replacing the damaged drive (data cannot be recovered
if both drives become damaged).
• RAID 1 mode
Arranges 2 hard drives in one array. You can create up to 2 RAID 1 arrays, with total usable space on each array being the
capacity of one of the drives. If either drive fails, data can be recovered by replacing the damaged drive (data cannot be
recovered if both drives become damaged). The other two drives not used in the RAID 1 array can be configured either
as a hot spare (which replaces any failed drive automatically), a second RAID 1 array, or as individual drives. Alternatively,
one may configured as an individual drive and the other a hot spare.
Note:
After replacing a failed drive in any of the above arrays, file 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".
TeraStation III iSCSI User Manual 17