Buffalo TeraStation HD-HTGL User Manual page 26

Note on RAID Arrays
TeraStation uses RAID RAID ("Redundant Array of Independent Disks") technology to control the four hard drives RAID
in your TeraStation. RAID may be confi gured several ways:
RAID Spanning RAID Spanning - All four drives are striped into one large drive, giving the maximum capacity for your RAID Spanning - All four drives are striped into one large drive, giving the maximum capacity for your
TeraStation. RAID Spanning is fast and effi cient, but has no redundancy. If one hard drive fails, all data on
the TeraStation is lost. This is how your TeraStation is set up out of the box.
RAID 1 (mirroring) - Hard drives (or spanned pairs of hard drives) are arranged in mirrored pairs. Each half
of the pair reads and writes exactly the same data. This costs you half the total capacity of your TeraStation,
but provides excellent redundancy. If a hard drive fails, the mirror continues to supply data, so you may work
on normally. You may replace the damaged or defective drive at any time, and normal RAID 1 mirroring will
then be automatically restored.
RAID 5 RAID 5 RAID 5 (parity) - All drives in a RAID 5 array reserve part of their data space for parity information, allowing (parity) - All drives in a RAID 5 array reserve part of their data space for parity information, allowing
all data to be recovered if a single drive fails. The parity information takes up about one hard drive's worth
of space, so if you set up all four drives in the TeraStation as a RAID 5 array, your usable capacity will be
about 3/4 of the total capacity of the TeraStation. RAID 5 is an excellent compromise between effi ciency
and security. If a single drive fails, no data is lost. After the damaged or defective drive is replaced, your
TeraStation will automatically restore all data to the new drive and resume normal RAID 5 operation.
Buffalo Technology recommends RAID 5 for its excellent balance of effi ciency and security.
("Redundant Array of Independent Disks") technology to control the four hard drives
RAID 5 RAID 5 for its excellent balance of effi ciency and security.
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