Quantum DLT 2000 Handbook page 102

RAIT systems work in essentially the same way as RAID. RAIT is
ranked by six increasing levels of security and capability from Level
0 to Level 5. For example, Level 1 RAIT provides disk mirroring in
which your data is written to two drives simultaneously. Each drive
contains the same data. This is known as disk mirroring or disk
duplexing. Should a drive fail for any reason, the other drive con-
tinues operation unaffected.
Level 3 and Level 5 RAIT use data striping, in which the data
stream is divided into equal parts, depending on how many drives
are in the array. In Level 3 RAIT, a drive is dedicated to maintain-
ing parity. This parity drive can sometimes cause a bottleneck
because all read/write requests must first go through the parity
drive. Should there be a drive failure, the parity information is
used to reconstruct the lost data.
Level 5 RAIT divides the parity information equally among all drives.
This type of system provides maximum data integrity, typically at the
expense of data throughput.
Disaster Recovery
Backup and archiving are not only important for the periodic
restoration of files that have been deleted or lost, but critical in dis-
aster recovery situations. Just because your business isn't located in
Tornado Alley or on a fault line in Missouri doesn't mean you
won't experience a "disaster."
In fact, most disasters are related to human error or system failure,
not natural disasters. Among the leading causes of business disrup-
tion are computer viruses, power outages, fire, vandalism, terror-
ism, and weather-related disasters.
QUANTUM DLTtape HANDBOOK 9.9