Advanced Host Controller Interface (AHCI) and Redundant Array of Independent Disks (RAID) on HP EliteDesk and EliteOne 705 Business PCs Using AMD Array Management Software (RAIDXpert2)

RAID 1 with two hard drives (Mirror)

RAID 1 has redundancy and hence is a true RAID, which greatly increases reliability. The probability of one hard drive

failure on a given day is the square root of the probability of both physical hard drives in the RAID 1 volume failing on a

given day. Hypothetically, if the chance for a single hard drive failure is 1:2000, then the chance that both hard drives

failing in RAID 1 is 1:4,000,000.

Mirroring, segmentation, and striping have no real meaning in RAID 1. In the table and graphic, the data is arranged in

rows for representation of different pieces of data.

Table 4: RAID 1 with two hard drives (Mirror)

First disk Second disk

Data Segment 5 Data Segment 5

Data Segment 6 Data Segment 6

Data Segment 7 Data Segment 7

Data Segment 8 Data Segment 8

In the previous table, each “Data Segment n” represents a group of data, known as a stripe. In this case, each row

represents a stripe. This table shows how information is duplicated in both hard drives. The size of the stripes is mostly

irrelevant and not a configurable option.

Because it is a very cost-effective way to increase system storage reliability and a great value proposition, RAID 1 is the

only RAID configuration that HP preconfigures for HP EliteDesk and EliteOne 705 Business PCs. RAID 1 provides high

availability with minimal performance impact, as well as greater reliability compared to a single hard drive

configuration.

To better illustrate the concept of RAID 1 and mirroring, Figure 3 shows how a sequence of data “ABCD...” is stored in a

RAID 1 volume. In this example, each letter represents a data segment. The graphic shows how the various pieces are

replicated for both of the hard drives; hence, if any one member of the RAID 1 volume fails, the information is kept in the

surviving members. After a hard drive failure, the user interface sends a notification so the failed hard drive can be

replaced. No user information is lost in this scenario.

Figure 2: RAID 1 with two hard drives