segments—or stripes—of data sequentially across the physical drives to create a large virtual drive. Data striping allows one of the drives to read data while

the other drive is searching for and reading the next block.

Another advantage of a RAID level 0 configuration is that it utilizes the full capacities of the drives. If you have two 120-GB drives installed, you have 240 GB

on which to store data.

NOTICE:

Because RAID level 0 provides no data redundancy, if one drive fails, then the data on the other drive is also inaccessible. Therefore, ensure

that you perform regular backups when you use a RAID level 0 configuration.

RAID Level 1

RAID level 1 uses a data-redundancy storage technique known as "mirroring." When data is written to the primary drive, the data is then duplicated—or

mirrored—on the other drive. A RAID level 1 configuration sacrifices high-data access rates for its data redundancy advantages.

If a drive failure occurs, subsequent read and write operations are directed to the surviving drive. A replacement drive can then be rebuilt using the data from

the surviving drive. Also, because data is duplicated on both drives, two 120-GB RAID level 1 drives collectively have a maximum of 120-GB on which to store

data.

RAID Level 5

RAID level 5 uses a data-staging storage technique known as "parity checking." When a block of data is written to the RAID configuration, it is striped across

all of the drives in the RAID array except for one drive, to which is written parity data. The parity data is information that allows for the entire block of striped

data to be calculated if one of the drives fails.

Since parity data is fairly small when compared to the size of the actual stored data, the equivalent of one hard drive can serve as a parity drive for any

number of data-storing hard drives. However, not all of the parity data is put on the same drive. Instead, with each new block of data written to the RAID

configuration, the different drives alternately act as either data-storing or parity drives.

Table of Contents