2 RAID technology overview

This chapter defines the terms used in this guide and describes the RAID technologies supported by select HP Business computers.

RAID terminology

Some of the terms in the following table have a broader meaning, but they are defined in relation to the RAID implementation described in this guide.

Term

Definition

 

 

Fault tolerance

The ability of the computer to continue to operate if one drive fails. Fault tolerance is

 

often used interchangeably with reliability, but the two terms are different.

 

 

HDD

One physical hard disk drive in the RAID array.

 

 

Option ROM

A software module inside the system's BIOS that provides extended support for a

 

particular piece of hardware. The RAID option ROM provides boot support for RAID

 

volumes as well as a user interface for managing and configuring the system's RAID

 

volumes.

 

 

Primary drive

The main internal hard drive in the computer.

 

 

RAID array

The physical drives that appear as one logical drive to the operating system.

 

 

RAID migration

The change of data from a non-RAID to RAID configuration. “RAID level migration,” or

 

the change of data from one RAID level to another, is not supported.

 

 

RAID volume

A fixed amount of space across a RAID array that appears as a single hard drive to the

 

operating system.

 

 

Recovery drive

The hard drive that is the designated mirror (copy of the primary) drive in a RAID 1 and

 

Recovery volume.

 

 

Reliability

The likelihood—over a period of time—that a hard drive can be expected to operate

 

without failure, also known as mean time before failure (MTBF).

 

 

Stripe

The set of data on a single hard drive in a RAID volume.

 

 

Striping

The distribution of data over multiple disk drives to improve read/write performance.

 

 

SSD (solid-state drive)

A solid-state drive is a flash-based or DRAM-based hard drive with no rotating media.

 

 

SED (self-encrypting drive)

A self-encrypting drive is a hard drive that uses hardware encryption to protect the data

 

on the drive.

 

 

mSATA module

An mSATA module is a flash-memory module with an mSATA connector.

 

 

RAID modes supported

The RAID modes supported by HP Business computers include RAID 0, RAID 1, RAID 5, and Flexible data protection (Recovery) as described below. RAID modes 0, 1, and Recovery require two SATA hard drives. RAID mode 5 requires three SATA hard drives. This can be accomplished by inserting a third SATA hard drive into the upgrade bay of specially-equipped computers. RAID 10 is not supported.

2 Chapter 2 RAID technology overview