Dell PowerVault MD3000, Hardware Owner'S Manual

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Using Your RAID Enclosure
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• Determine which hosts you want to grant access to which virtual disks, then create mappings to
associate the virtual disks with the hosts.
NOTE:
Host access must be created prior to mapping virtual disks to them.
Disk groups are always created in the unconfigured capacity of a storage array; virtual disks are created
within the free capacity of a disk group.
Unconfigured capacity is comprised of the available physical disk
space that is not already assigned in the storage array. Free capacity is the space in a disk group that has
not been assigned to a virtual disk.
Creating a Virtual Disk
To create a virtual disk, use one of the following methods:
• Create a new disk group from unconfigured capacity. You can define the RAID level and capacity (the
number of physical disks) for the disk group, then define the parameters for the first virtual disk in the
new disk group.
• Create a new virtual disk in the free capacity of an existing disk group. You only need to specify the
parameters for the new virtual disk.
Virtual Disk States
The RAID controller module recognizes the following virtual disk states.
Supported RAID Levels
RAID levels determine the way in which data is written to physical disks. Different RAID levels provide
different levels of accessibility, redundancy, and capacity.
Using multiple physical disks has several advantages over using a single physical disk, including:
• Placing data on multiple physical disks, called striping , means that input/output (I/O) operations can
occur simultaneously and improve performance.
• Storing redundant data on multiple physical disks using mirroring or parity supports reconstruction of
lost data if an error occurs, even if that error is the failure of a physical disk.
Table 3-2. RAID Controller Virtual Disk States
State Description
Optimal The virtual disk contains physical disks that are all online.
Degraded The virtual disk with a redundant RAID level contains an inaccessible physical disk.
The system can still work properly, but performance may be affected and additional
disk failures may result in data loss.
Offline A virtual disk with one or more member disks in an inaccessible (failed, missing, or
offline) state. Data on the virtual disk is no longer accessible.