Using Snapshot And Disk Copy Together; Hardware Redundancy And Failover; Redundancy And Non-Redundancy; Multi-Path Software - Dell PowerVault MD3000 Hardware Owner's Manual

Using Snapshot and Disk Copy Together

You can use the Snapshot Virtual Disk and Virtual Disk Copy premium features together to back up data
on the same storage array, or to restore the data on the snapshot virtual disk to its original source virtual
disk.
You can copy data from a virtual disk in one of two ways:
• By taking a point-in-time snapshot of the data
• By copying the data to another virtual disk using a virtual disk copy
You can select a snapshot virtual disk as the source virtual disk for a virtual disk copy. This configuration
is one of the best ways you can apply the snapshot virtual disk feature, since it enables complete backups
without any impact to the storage array I/O.
You cannot, however, use a snapshot repository virtual disk as a source virtual disk or as a target virtual
disk in a virtual disk copy. If you select the source virtual disk as the target virtual disk of a virtual disk
copy, you must disable all snapshot virtual disks associated with the source virtual disk.

Hardware Redundancy and Failover

This section provides basic information that will help you determine how to connect a host to the RAID
controller modules in a RAID enclosure in order to achieve redundancy and failover.
NOTE:
The best practice for ensuring data access is to avoid a configuration with a single point of failure. A single
point of failure is any component or path that is not duplicated (redundant) or whose failure can cause loss of data
access.

Redundancy and Non-Redundancy

Redundancy means that a storage array has duplicate components, or alternate ways to provide essential
services. This redundancy ensures access to the virtual disks in case of a failure of a single component.
In a typical RAID configuration, most of the components are redundant; however, the configuration
itself might not be fully redundant. For example, there might be components whose individual failure
would cause loss of access to the virtual disks. In a fully redundant storage array, all components must be
duplicated. In addition, the storage array must be configured in such a way as to ensure that duplicate
components can be accessed in case of a failure.

Multi-Path Software

Multi-path software (also referred to as the failover driver) is software resident on the host server that
provides management of the redundant data path between the server and the RAID enclosure. For the
multi-path software to correctly manage a redundant path, the configuration must provide for redundant
HBAs and cabling.
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Using Your RAID Enclosure