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Appendix C: RAID Basics
Overview
A Redundant Array of Independent Disks (RAID) is an array of several hard disks
that provide data security and high performance. A RAID system accesses several
hard disks simultaneously, which improves I/O performance over a single hard
disk. Data security is enhanced by a RAID, since data loss due to a hard disk
failure is minimized by regenerating redundant data from the other RAID hard
disks.
Benefits
RAID improves I/O performance, and increases data security through fault
tolerance and redundant data storage.
Improved Performance
RAID provides access to several hard disk drives simultaneously, which greatly
increases I/O performance.
Data Security
Hard disk drive failure unfortunately is a common occurrence. A RAID helps
prevent against the loss of data due to hard disk failure. A RAID offers additional
hard disk drives that can avert data loss from a hard disk drive failure. If a hard
drive fails, the RAID volume can regenerate data from the data and parity stored
on its other hard disk drives.
RAID Levels
The Thecus 1U4500 supports standard RAID levels 0, 1, 5, 6, 10, and JBOD. You
choose a RAID level when you create a system volume. The factors for selecting a
RAID level are:
• Your requirements for performance
• Your need for data security
• Number of hard disk drives in the system, capacity of hard disk drives in
the system
The following is a description of each RAID level:
RAID 0
RAID 0 is best suited for applications that need high bandwidth but do not require
a high level of data security. The RAID 0 level provides the best performance of
all the RAID levels, but it does not provide data redundancy.
RAID 0 uses disk striping and breaking up data into blocks to write across all hard
drives in the volume. The system can then use multiple hard drives for faster
read and write. The stripe size parameter that was set when the RAID was
created determines the size of each block. No parity calculations complicate the
write operation.