Installation guide

Chapter 1. Introduction
17
1.2.8 JBOD
(Just a Bunch Of Disks) A group of hard disks in a RAID subsystem are not set
up as any type of RAID configuration. All drives are available to the operating
system as an individual disk. JBOD does not provide data redundancy.
1.2.9 Single Disk (Pass-Through Disk)
Pass through disk refers to a drive that is not controlled by the RAID firmware
and thus can not be a part of a RAID volume. The drive is available to the
operating system as an individual disk.
1.2.10 Summary of RAID Levels
RAID subsystem supports RAID Levels 0, 1, 10(1E), 3, 5, 6, 30, 50 and 60. The
following table provides a summary of RAID levels.
Feature and Performance
RAID
Level
Description
Disks
requirement
(Cost)
Data Reliability
Data Transfer
Rate
I/O Request
Rates
0
Also known as stripping.
Data distributed across multiple drives in
the array. There is no data protection
N
* No data
Protection.
Very High
Very High for
Both Reads and
Writes
1 Also known as mirroring.
All data replicated on N Separated disks.
N is almost always 2.
This is a high availability
Solution, but due
to the 100% duplication, it is also a costly
solution.
2
* Lower than
RAID 6.
* Higher than
RAID3,5
Reads are
Higher Than a
single disk;
Writes similar to
a single disk.
Reads are twice
faster than a
single disk;
Write are similar
to a single disk.
10
(1E)
Also known Block-Interleaved Parity.
Data and parity information is subdivided
and distributed across all disk. Parity must
be the equal to the smallest disk capacity
in the array. Parity information normally
stored on a dedicated parity disk.
N (N>2)
* Lower than
RAID 6.
* Higher than
RAID3,5
Transfer rates
more similar to
RAID 1 than
RAID 0
Reads are twice
faster than a
single disk;
Write are similar
to a single disk.
3 Also known Bit-Interleaved Parity.
Data and parity information is subdivided
and distributed across all disk. Parity must
be the equal to the smallest disk capacity
in the array. Parity information normally
stored on a dedicated parity disk.
N+1
* Lower than
RAID 1, 10,
and 6.
* Higher than a
single drive.
Reads are
similar to RAID
0;
Writes are
slower than a
single disk.
Reads are
similar twice
faster than a
single disk;
Write are similar
to a single disk.