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8 Introduction
Introduction to Storage Arrays
A storage array includes various hardware components, such as physical disks, RAID controller modules,
fans, and power supplies, gathered into enclosures. An enclosure containing physical disks accessed
through RAID controller modules is called a RAID enclosure.
One or more host servers attached to the storage array can access the data on the storage array. You can
also establish multiple physical paths between the host(s) and the storage array so that loss of any single
path (through failure of a host server port, for example) does not result in total loss of access to data on the
storage array.
The storage array is managed by MD Storage Manager software running either on a host server or a
dedicated management station. On a host server system, MD Storage Manager and the storage array
communicate management requests and event information directly via iSCSI ports. On a dedicated
management station, MD Storage Manager communicates with the storage array either through an
Ethernet connection on the RAID controller modules or via the host agent installed on the host server.
Using MD Storage Manager, you configure the physical disks in the storage array into logical components
called disk groups, then divide the disk groups into virtual disks. You can make as many disk groups and
virtual disks as your storage array configuration and hardware permit. Disk groups are created in the
unconfigured capacity of a storage array, while virtual disks are created in the free capacity of a disk
group.
Unconfigured capacity is comprised of the physical disks not already assigned to a disk group. When a
virtual disk is created using unconfigured capacity, a disk group is automatically created. If the only
virtual disk in a disk group is deleted, the disk group is also deleted. Free capacity is space in a disk group
that has not been assigned to a virtual disk.
Data is written to the physical disks in the storage array using RAID technology. RAID levels define the
way in which data is written to physical disks. Different RAID levels offer different levels of accessibility,
redundancy, and capacity. You can set a specified RAID level for each disk group and virtual disk on your
storage array.
You can also provide an additional layer of data redundancy by creating disk groups that have a RAID
level other than 0. Hot spares can automatically replace physical disks marked as Failed.
For more information on using RAID and managing data in your storage solution, see the Dell™
PowerVault™ Modular Disk Storage Manager User’s Guide.