What are the common storage device categories? What are the different?

What are the functions of RAID?

What are the common RAID Levels? What are the technical priciples?

What are the advantages of Multipathing?

What is the principle of snapshot? What are the applications of snapshot?

Raid increases the data read efficiency and also provides the data backup function (True or false)

What are the common storage device categories?
a) DAS
b) SAS
c) NAS
d) SAN