ATTO Technology Diamond Storage Array S-Class - Manual (Page 61)

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Configuring drives
RAID Level 10 is used in applications requiring
high performance and redundancy, combining the
attributes of RAID Levels 1 and 0.
The QuickRAID10 command, accessed through
the Command Line Interface, allows a simple,
out-of-the-box setup of RAID Level 10 groups.
The array will operate in degraded mode if a drive
fails unless you have enabled Hot Spare sleds.
RAID Level 5
RAID Level 5 increases reliability while using
fewer disks than mirroring by employing parity
redundancy. Distributed parity on multiple drives
provides the redundancy to rebuild a failed drive
from the remaining good drives. Parity data is
added to the transmitted data at one end of the
transaction, then the parity data is checked at the
other end to make sure the transmission has not
had any errors.
In the array, transmitted data with the added parity
data is striped across disk drives. A hardware
XOR engine computes parity, thus alleviating
software processing during reads and writes.
The array will operate in degraded mode if a drive
fails unless you have enabled Hot Spare sleds.
Interleave
The interleave size sets the amount of data to be
written to each drive in a RAID group. This is a
tunable parameter which takes a single stream of
data and breaks it up to use multiple disks per I/O
interval.
The CLI command RAIDInterleave allows you
to change the size of the sector interleave between
RAID groups. The value will depend upon the
normal expected file transfer size. If the normal
file transfer size is large, the interleave value
should be large, and vice versa.
The value entered for the RAIDInterleave
command refers to blocks of data: one block is
equivalent to 512 bytes of data.
Valid entries are 16, 32, 64, 128, 256 and SPAN.
SPAN, not available in RAID Level 5, indicates
that interleave size between the drives in the
group will be the minimum drive size of all
members in the group.
Hot Spare sleds
In most configurations, if a member of a virtual
device becomes degraded, you must swap out the
faulted sled as defined in
Hot Swap Operating
Instructions on page 71 . If you have not enabled
AutoRebuild , you must also start a manual rebuild.
For four configurations, however, Hot Spare sleds
may be designated as replacements for faulted
sleds without intervention by you or a host.
Each configuration requires a certain number of
Hot Spare sleds. These sleds, once designated as
Hot Spares, are not available for other use.
The following configurations will support
optional Hot Spare sleds
RAID Level 1: 2 Hot Spare sleds
RAID Level 10: 1 group, 2 Hot Spare sleds
RAID Level 5: 1 group, 1 Hot Spare sled
RAID Level 5: 2 groups, 2 Hot Spare sleds
Enhancing performance
SpeedWrite, enabled by the CLI command
SpeedWrite, improves the performance of
WRITE commands