Raid - IBM V7000 Introduction And Implementation Manual

Important: From IBM Flex System V7000 Storage Node code version 6.4 onwards, the
layer parameter can only be changed by running chsystem using the CLI. The default is
the storage layer, and you must change it to replication if you need to set up a copy
services relationship between IBM Flex System V7000 Storage Node with either the IBM
Storwize V7000 or SAN Volume Controller.
As mentioned earlier, one canister is designated as the configuration node and it is the
canister that activates the system IP address. If the configuration node fails, the system
chooses a new canister as the configuration node and the new canister takes over the system
IP addresses.
The system can be configured using either IBM Flex System V7000 Storage Node
management software or the command-line interface (CLI),

2.6.5 RAID

The IBM Flex System V7000 Storage Node setup contains a number of internal disk drive
objects known as candidate drives, but these drives cannot be directly added to storage
pools. The drives need to be included in a Redundant Array of Independent Disks (RAID)
grouping used for performance and to provide protection against the failure of individual
drives.
These drives are referred to as members of the array. Each array has a RAID level. Different
RAID levels provide different degrees of redundancy and performance, and have different
restrictions regarding the number of members in the array.
IBM Flex System V7000 Storage Node supports hot spare drives. When an array member
drive fails, the system automatically replaces the failed member with a hot spare drive and
rebuilds the array to restore its redundancy (the exception being RAID 0). Candidate and
spare drives can be manually exchanged with array members.
Each array has a set of goals that describe the wanted location and performance of each
array. A sequence of drive failures and hot spare takeovers can leave an array unbalanced,
that is, with members that do not match these goals. The system automatically rebalances
such arrays when the appropriate drives are available.
The following RAID levels are available:
RAID 0 (striping, no redundancy)
RAID 1 (mirroring between two drives)
RAID 5 (striping, can survive one drive fault)
RAID 6 (striping, can survive two drive faults)
RAID 10 (RAID 0 on top of RAID 1)
RAID 0 arrays stripe data across the drives. The system supports RAID 0 arrays with just one
member, which is similar to traditional JBOD attach. RAID 0 arrays have no redundancy, so
they do not support hot spare takeover or immediate exchange. A RAID 0 array can be
formed by one to eight drives.
RAID 1 arrays stripe data over mirrored pairs of drives. A RAID 1 array mirrored pair is rebuilt
independently. A RAID 1 array can be formed by two drives only.
RAID 5 arrays stripe data over the member drives with one parity strip on every stripe. RAID 5
arrays have single redundancy. The parity algorithm means that an array can tolerate no more
than one member drive failure. A RAID 5 array can be formed by 3 to 16 drives.
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IBM Flex System V7000 Storage Node Introduction and Implementation Guide