6
The HP Compaq dc5850 Microtower also allows for RAID 0 with three hard drives. However, reliability is
less than a RAID 0 configuration with two hard drives.
RAID 0 with three hard drives is shown in the following figure:
Figure 2 RAID 0 - Three hard drives
RAID 1 with two hard drives (Mirror)
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 Compaq dc5850 Business PCs. RAID
1 provides high availability with minimal performance impact, as well as greater reliability compared to
a single hard drive configuration.
RAID 1 has redundancy and hence is a true RAID. It more than doubles reliability because the MTBF of
RAID 1 is equal to the MTBF of an individual drive multiplied by the number of drives (2). In other words,
the probability of one hard drive failure on a given day is the square root of that same probability. Hypo-
thetically, if the chances that a single hard drive fails is 1:2000, with RAID 1 the chance that both of your
hard drives fail 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 1 Data Segment 1
Data Segment 2 Data Segment 2
Data Segment 3 Data Segment 3
Data Segment 4 Data Segment 4
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