ERQ12-U4R2 & ERQ12-F2R2
Serial ATA Disk Array Systems
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Summary of RAID Levels
The following table summarizes the performance characteristics of each RAID level. A high
availability or access rate number indicates high availability or quick access rate.
Array
Group
Availability
Access
Rate
Capacity
Utilization
Description
NRAID
1
1
100%
Sum of all disks in the array
JBOD
1
1
100%
Data is distributed by filling each
disk in turn.
RAID 0
1
5
100%
Data is divided into pieces and
written to all disks in parallel.
RAID 1
5
2
50%
Data is duplicated on both disks.
RAID 3
3
3
Between 67%
for 3 disks to
94% for 16
disks
Data is divided into pieces; the
parity of these pieces is calcu-
lated; and the pieces are written
to separate disks in parallel with
the writing of the parity to a dedi-
cated disk.
RAID 5
3
3.5
Between 67%
for 3 disks to
94% for 16
disks
Data is divided into pieces; the
parity of these pieces is calcu-
lated; and the pieces and parity
are written to separate disks in
parallel. The parity is written to a
different disk each time.
RAID 0+1
4.5
5
50%
RAID 0+1 is a RAID 1 consisting
of RAID 0 members.
RAID 30
4
4
Between 67%
for 6 disks to
88% for 16
disks
RAID 30 is a RAID 0 consisting
of RAID 3 members.
RAID 50
4
4.5
Between 67%
for 6 disks to
88% for 16
disks
RAID 50 is a RAID 0 consisting
of RAID 5 members.
