Host Types; Snapshot Virtual Disks - Dell PowerVault MD3000 Hardware Owner's Manual

You can manually configure a host-to-virtual disk mapping. When you configure host-to-virtual disk
mapping, consider these guidelines:
• You can define one host-to-virtual disk mapping for each virtual disk in the storage array.
• Host-to-virtual disk mappings are shared between RAID controller modules in the storage array.
• A unique LUN must be used by a host group or host to access a virtual disk.
• Not every operating system will have the same number of LUNs available for use.

Host Types

Generally, a host is a server that accesses a storage array, is mapped to the virtual disks, and uses one or
more HBA ports. In general, hosts have the following attributes:
• Host name - A name that uniquely identifies the host.
• Host group (used in Cluster solutions only) - Two or more hosts associated together to share access to
the same virtual disks.
A host group is a group of two or more hosts that share access to specific virtual disks on the storage
array. This is a logical entity you can create in MD Storage Manager. All hosts in a host group must be
running the same operating system.
• Host type - The operating system running on the host.
• HBA host port - A physical connection on the host base adapter installed in the host.
HBA host ports are automatically detected by the host agent and can be identified by an alias assigned
by the user.

Snapshot Virtual Disks

A snapshot is a point-in-time image of a virtual disk. The snapshot provides an image of the virtual disk
at the time the snapshot was created. Typically, you create a snapshot so that an application (for example,
a backup application) can access the snapshot and read the data while the source virtual disk remains
online and user-accessible. When the backup is completed, the snapshot virtual disk is no longer needed.
Another potential use would be to experiment with a few different configurations until you determine
which one is the best. You can create up to four snapshots per virtual disk.
Snapshots are used to recover previous versions of files that have changed since the snapshot was taken.
Snapshots are implemented using a copy-on-write algorithm. Data on a virtual disk is copied to the
snapshot repository before it is modified.
Snapshots are instantaneous and take up less overhead than a full physical copy process.
For further details on using snapshot virtual disks, see the MD Storage Manager User's' Guide.
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Using Your RAID Enclosure