HP PRINTER SERIES D2600, Руководство пользователя

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RAID meth-
od Data redund-
ancy Best practices Summary
Striping None
IMPORTANT : Do not use RAID0
for LUNs if fault tolerance is re-
quired. Consider RAID0 only for
noncritical storage. RAID0 LUNs
provide the best performance for
applications that use random I/O.
RAID0 is optimized for I/O
speed and efficient use of
physical disk capacity, but
provides no data redund-
ancy.
RAID0
Mirroring High
In general, RAID1 virtual disks
provide better performance char-
acteristics over a wider range of
application workloads than
RAID5.
RAID1 is optimized for data
redundancy and I/O speed,
but uses the most physical
disk space.
IMPORTANT :
RAID1 uses about 100%
more physical disk space
than RAID0 and 70% more
than RAID5.
RAID1
Striping and
parity
Medium
RAID5 virtual disks can provide
performance advantages over
RAID1 for some applications that
use sequential I/O. Consider
RAID5 disks for applications with
high sequential I/O of records in
multiples of 8K bytes. The larger
the record size, the greater the
advantage.
RAID5 provides a balance
of data redundancy, I/O
speed and efficient use of
physical disk space.
RAID5
Striping and
parity
High
RAID6 is most useful when data
loss is unacceptable but cost is
also an important factor. The
probability that data loss will oc-
cur when an array is configured
with RAID6 is less than it would
be if it was configured with
RAID5. However, write perform-
ance is lower than RAID5 be-
cause of the two sets of parity
data.
Like RAID5, RAID6 gener-
ates and stores parity inform-
ation to protect against data
loss caused by drive failure.
With RAID6, however, two
different sets of parity data
are used, allowing data to
be preserved if two drives
fail.
RAID6
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.
Spare disks
Spares are disks that are not active members of any particular array, but have been configured to
be used when a disk in one of the arrays fails. If a spare is present, it will immediately be used to
begin rebuilding the information that was on the failed disk, using parity information from the other
member disks. During the rebuilding process, the array is operating in a reduced state and, unless it
is a RAID6 or RAID1+0 array, it cannot tolerate another disk failure in the same array. If another disk
D2600/D2700 Disk Enclosure User Guide 27