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 use of
RAID0
Consider RAID0 only for noncriticalphysical disk capacity, but
provides no data redundancy. storage. RAID0 LUNs provide the
best performance for applications
that use random I/O.
MirroringHighIn general, RAID1 virtual disks
provide better performance
RAID1 is optimized for data
redundancy and I/O speed,
RAID1
characteristics over a wider rangebut uses the most physical
of application workloads than
RAID5.
disk space. IMPORTANT:
RAID1 uses about 100% more
physical disk space than
RAID0 and 70% more than
RAID5.
Striping and
parity
MediumRAID 50 tolerates one drive failure
in each spanned array without loss
RAID5 protects against failure
of one drive (and failure of
RAID5
of data. RAID 50 requires lessparticular multiple drives).
rebuild time than single RAID 5RAID 50 is a nested RAID
arrays RAID 50 requires a minimum
of six drives.
method that uses RAID 0
striping across RAID 5 arrays.
Striping and
parity
HighRAID6 is most useful when data loss
is unacceptable but cost is also an
RAID6+0 allows
administrators to split the
RAID6
important factor. The probability thatRAID 6 storage across
data loss will occur when an arraymultiple external boxes. RAID
is configured with RAID6 is less than60 requires a minimum of
it would be if it was configured witheight drives. RAID 60 is a
RAID5. However, write performancenested RAID method that uses
is lower than RAID5 because of the
two sets of parity data.
RAID 0 block-level striping
across multiple RAID 6 arrays
with dual distributed parity.
With the inclusion of dual
parity, RAID 60 will tolerate
the failure of two disks in each
spanned array without loss of
data.
Striping and
parity
HighOrganizations implementing a large
drive array should consider RAID 6
Allocates the equivalent of two
parity drives across multiple
RAID6
with
because it can tolerate up to twodrives and allowsAdvance
simultaneous drive failures without
downtime or data loss.
simultaneous write operations
Distributed Data Guarding
Data
Guarding
(ADG) (RAID 5): Allocates parity data
across multiple drives and
allows simultaneous write
operations. Drive Mirroring
(RAID 1 and 1+0 Striped
Mirroring): Allocates half of the
drive array to data and the
other half to mirrored data,
providing two copies of every
file
Disk drive sizes and types
RAID arrays should be composed of disk drives of the same size and performance capability.
When drives are mixed within a disk enclosure, the usable capacity and the processing ability
of the entire storage sub-system is affected. For example, when a RAID array is composed of
different sized drives, the RAID array defaults to the smallest individual drive size, and capacity
in the larger drives goes unused.
Preliminary tasks 25
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