HP 381513-B21 - Smart Array P800 Controller RAID Technology Brief page 4

Table 1. Summary of RAID technologies for large arrays
RAID LEVELS
RAID 0
Requires a minimum of one drive.
RAID 1
Requires a minimum of two drives.
RAID 1+0
Requires a minimum of four drives.
RAID 5
Requires a minimum of three drives.
Pn represents one set of parity.
RAID 6 (ADG)
Requires a minimum of four drives.
Pn and Qn represent two sets of parity.
Function/Applications
Data is distributed
across separate disk
drives.
Image Editing • Video
Production • Pre-Press
Applications
Mirroring - Identical
data stored on two
drives, high fault
tolerance, very good
performance (higher
read performance than
RAID 0).
Accounting • Payroll •
Financial
Implemented as striped,
mirrored disks.
Database applications
requiring high
performance and fault
tolerance; sacrifices
storage efficiency.
One set of parity data
is distributed across all
drives. Protects against
the failure of any one
drive in an array.
Transaction processing
• File and application
servers • ERP • Internet
and Intranet servers
Two sets of parity data
are distributed across
all drives. Protects
against the failure of
two drives in an array.
Provides higher fault
tolerance than RAID 5.
For 24x7 applications
that require a higher
level of fault tolerance
than RAID 5.
Limitations
Highly vulnerable
to failure. The
entire array will
fail if one drive
fails.
50% of capacity
dedicated to fault
protection.
Doubles the
number of drives
required.
Potentially risky
for large arrays.
Can only
withstand the loss
of one drive
without total
array failure. Low
write
performance
(improved with
battery-backed
cache).
Lower write
performance than
other RAID levels.
Sequential and
burst-write
performance can
be much
improved with
battery-backed
cache.
4