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.

Because data is striped across the RAID configuration, as it is in a RAID 0 configuration, it can be quickly accessed. Also, because of the parity data, if only a

single drive fails, that drive can be rebuilt using the parity data on the other drives. The amount of storage space available to three 120-GB RAID level 5 drives

is 240-GB on which to store data, since the equivalent of one drive is set aside for parity data. A minimum of three drives is required to create a RAID level 5

configuration.

RAID Level 10

NOTE:

RAID levels 5 and 10 are only available via an optional PCI Express RAID controller card.

RAID level 10 uses a combination of striping and mirroring methods. It requires four drives. The drives are broken up into mirroring pairs and then the data

that is written to the RAID configuration is striped across all four drives. Data can be accessed quickly, due to the striping of data, however each piece of data

is duplicated on another drive, for redundancy purposes.

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

data from the surviving drives. Also, because data is duplicated on the primary and additional drives, four 120-GB RAID level 1 drives collectively have a

maximum of 240-GB on which to store data.

Configuring Your Computer for RAID

At some point you may want to configure your computer for RAID if you did not select a RAID configuration when you purchased your computer. You must have

at least two hard drives installed in your computer to set up a RAID configuration. For instructions on how to install a hard drive, see

(Hard Drive Bays

1-4).

RAID Configuration Utility

Installing a Hard Drive

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