Appendix B: Raid Basics; Ove R Vie; Be N E Fit; Improved Performance - Thecus N8900 series User Manual

Appendix B: RAID Basics

Overview
A Redundant Array of I ndependent Disks ( RAI D) is an array of sev eral hard disks
t hat provide dat a securit y and high perform ance. A RAI D syst em accesses sev eral
hard disks sim ult aneously, which im proves I / O per form ance over a single hard disk.
Dat a securit y is enhanced by a RAI D, since dat a loss due t o a hard disk failure is
m inim ized by r egenerat ing redundant dat a fr om t he ot her RAI D hard disks.
Benefits
RAI D im proves I / O perform ance, and increases dat a securit y t hrough fault
t olerance and r edundant dat a st orage.

Improved Performance

RAI D pr ovides access t o several hard disk drives sim ult aneously, which great ly
increases I / O perfor m ance.

Data Security

Hard disk drive failure unfort unat ely is a com m on occur r ence. A RAI D helps prevent
against t he loss of dat a due t o hard disk failure. A RAI D offer s addit ional hard disk
drives t hat can avert dat a loss from a hard disk drive failure. I f a hard drive fails,
t he RAI D volum e can r egenerat e dat a from t he dat a and parit y st or ed on it s ot her
hard disk drives.
RAID Levels
The Thecus I P st orage support s st andard RAI D lev els 0, 1, 5, 6, 10, 50, 60 and JBOD.
You choose a RAI D lev el when y ou creat e a sy st em v olum e. The fact ors for
select ing a RAI D level are:
•
Your r equirem ent s for per form ance
•
Your need for dat a securit y
•
Num ber of hard disk drives in t he sy st em , capacit y of hard disk drives in t he
syst em
The following is a descript ion of each RAI D lev el:
RAI D 0
RAI D 0 is best suit ed for applicat ions t hat need high bandwidt h but do not r equire
a high level of dat a securit y. The RAI D 0 lev el provides t he best per form ance of all
t he RAI D lev els, but it does not provide dat a r edundancy.
RAI D 0 uses disk st riping and breaking up dat a int o blocks t o w rit e across all hard
drives in t he v olum e. The sy st em can t hen use m ult iple hard drives for fast er r ead
and writ e. The st ripe size par am et er t hat was set when t he RAI D was creat ed
det erm ines t he size of each block. No parit y calculat ions com plicat e t he writ e
operat ion.
RAI D 1
RAI D 1 m irrors all dat a from one hard disk drive t o a second one hard disk drive,
t hus providing com plet e dat a r edundancy. How ev er, t he cost of dat a st orage
capacit y is doubled.
204