Dell UCS-51, User Manual

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10
Overview
About RAID
RAID is a group of multiple independent physical disks that provide high performance by increasing the
number of drives used for saving and accessing data. A RAID disk subsystem improves I/O performance
and data availability. The physical disk group appears to the host system as a single storage unit or as
multiple logical units. Data throughput improves because multiple disks can be accessed simultaneously.
RAID systems also improve data storage availability and fault tolerance.
RAID Levels
Integrated Striping or RAID 0 uses disk striping to provide high data throughput, especially for large files
in an environment that requires no data redundancy.
Integrated Mirroring or RAID 1 uses disk mirroring so that data written to one physical disk is
simultaneously written to another physical disk. This is good for small databases or other applications
that require small capacity, but complete data redundancy.
NOTICE:
Lost data on an Integrated Striping virtual disk cannot be recovered in the event of a physical disk failure.
RAID Terminology
Integrated Striping
Integrated Striping (RAID 0) allows you to write data across multiple physical disks instead of just one
physical disk. Integrated Striping involves partitioning each physical disk storage space into 64 KB stripes.
These stripes are interleaved in a repeated sequential manner. The part of the stripe on a single physical
disk is called a stripe element.
For example, in a four-disk system using only Integrated Striping, segment 1 is written to disk 1, segment 2
is written to disk 2, and so on. Integrated Striping enhances performance because multiple physical disks
are accessed simultaneously, but Integrated Striping does not provide data redundancy. Figure 1-2 shows
an example of Integrated Striping.
Figure 1-2. Example of Integrated Striping (RAID 0)
Stripe element 1
Stripe element 5
Stripe element 9 Stripe element 2
Stripe element 6
Stripe element 10
Stripe element 3
Stripe element 7
Stripe element 11
Stripe element 4
Stripe element 8
Stripe element 12
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