Chapter 1. Overview of the IBM Storwize V5000 Gen2 system 21
1.6.4 Clustered system
A clustered system consists of one or two pairs of node canisters. Each pair forms an I/O
group. All configuration, monitoring, and service tasks are performed at the system level. The
configuration settings are replicated across all node canisters in the clustered system. To
facilitate these tasks, one or two management IP addresses are set for the clustered system.
By using this configuration, you can manage the clustered system as a single entity.
A process exists to back up the system configuration data on to disk so that the clustered
system can be restored in a disaster. This method does not back up application data. Only
IBM Storwize V5000 Gen2 system configuration information is backed up.
The system can be configured by using the IBM Storwize V5000 Gen2 management software
(GUI), CLI, or USB key.
1.6.5 RAID
The IBM Storwize V5000 Gen2 contains several internal drive objects, but these drives
cannot be directly added to the storage pools. Drives need to be included in a Redundant
Array of Independent Disks (
RAID) 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. RAID
levels provide various degrees of redundancy and performance. The maximum number of
members in the array varies based on the RAID level.
Traditional RAID (TRAID) has the concept of 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. Candidate and spare drives can be manually exchanged
with array members.
Apart from traditional disk arrays, IBM Spectrum™ Virtualize V7.6 introduced Distributed
RAIDs. Distributed RAID improves recovery time of failed disk drives in an array by the
distribution of spare capacity between primary disks, rather than dedicating a whole spare
drive for replacement.
Details about traditional and distributed RAID arrays are described in Chapter 4, “Storage
pools” on page 143.
1.6.6 Managed disks
A managed disk (MDisk) refers to the unit of storage that IBM Storwize V5000 Gen2
virtualizes. This unit can be a logical volume on an external storage array that is presented to
the IBM Storwize V5000 Gen2 or a (traditional or distributed) RAID array that consists of
internal drives. The IBM Storwize V5000 Gen2 can then allocate these MDisks into storage
pools.
An MDisk is invisible to a host system on the storage area network because it is internal to the
IBM Storwize V5000 Gen2 system. An MDisk features the following modes:
System configuration backup: After the system configuration is backed up, save the
backup data on to your local hard disk (or at the least outside of the SAN). If you are unable
to access the IBM Storwize V5000 Gen2, you do not have access to the backup data if it is
on the SAN. Perform this configuration backup after each configuration change to be safe.
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