Chassis Install Instructions (734751-001, March 2014)

Striping methods
There are two methods for configuring the physical layout of the disk arrays:
• Vertical striping—the RAID array uses one physical drive from each disk enclosure.
• Horizontal striping—the RAID array uses multiple drives contained within one or more disk
enclosures.
RAID levels
Controllers use RAID technology to group multiple disk drives together in larger logical units (LUNs).
Key RAID methods include the use of data striping, data mirroring, and parity error checking. Data
striping improves speed by performing virtual disk I/O with an entire group of physical disks at
the same time. Mirroring provides data redundancy by storing data and a copy of the data. Parity
error checking provides automatic detection and correction if corruption of a physical disk occurs.
Depending on the host environment, the following RAID levels are supported with this disk enclosure:
RAID0, RAID1, RAID5 and RAID6 with ADG. Each level uses a different combination of RAID
methods that impact data redundancy, the amount of physical disk space used, and I/O speed.
After you create a LUN, you cannot change the RAID level.
The following table compares the different RAID levels.
RAID methodData redundancyBest practicesSummary
StripingNoneIMPORTANT: Do not use RAID0 for
LUNs if fault tolerance is required.
RAID0 is optimized for
I/O speed and efficient
RAID0
Consider RAID0 only for noncriticaluse of physical disk
storage. RAID0 LUNs provide thecapacity, but provides
no data redundancy. best performance for applications
that use random I/O.
MirroringHighIn general, RAID1 virtual disks
provide better performance
RAID1 is optimized for
data redundancy and
RAID1
characteristics over a wider rangeI/O speed, but uses the
of application workloads than
RAID5.
most physical disk
space. IMPORTANT:
RAID1 uses about 100%
more physical disk space
than RAID0 and 70%
more than RAID5.
Striping and parityMediumRAID5 virtual disks can provide
performance advantages over
RAID5 provides a
balance of data
RAID5
RAID1 for some applications thatredundancy, I/O speed
use sequential I/O. Consider RAID5and efficient use of
physical disk space. disks for applications with high
sequential I/O of records in
multiples of 8K bytes. The larger the
record size, the greater the
advantage.
Striping and parityHighRAID6 is most useful when data loss
is unacceptable but cost is also an
Like RAID5, RAID6
generates and stores
RAID6
important factor. The probabilityparity information to
that data loss will occur when anprotect against data loss
array is configured with RAID6 iscaused by drive failure.
less than it would be if it wasWith RAID6, however,
configured with RAID5. However,two different sets of
write performance is lower thanparity data are used,
RAID5 because of the two sets of
parity data.
allowing data to be
preserved if two drives
fail.
10 Installing the enclosure