Host Types; Advanced Features; Snapshot Virtual Disks; Snapshot Repository Virtual Disk - Dell PowerVault MD3260i Administrator's Manual

Host Types

A host server is a server that accesses a storage array. Host servers are mapped to the virtual disks and use one or
more iSCSI initiator ports. Host servers have the following attributes:
• Host name — A name that uniquely identifies the host server.
• Host group (used in Cluster solutions only) — Two or more host servers associated together to share access to
the same virtual disks.
NOTE: This host group is a logical entity you can create in the MD Storage Manager. All host servers in a
host group must be running the same operating system.
• Host type — The operating system running on the host server.

Advanced Features

The RAID enclosure supports several advanced features:
• Virtual Disk Snapshots
• Virtual Disk Copy
• High Performance Tier
• Remote replication (applicable to Dell PowerVault MD3660f storage arrays that support the FC protocol.)
NOTE: The premium features listed above must be activated separately. If you have purchased these features, an
activation card is supplied that contains instructions for enabling this functionality.

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. 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. 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, which makes a backup copy of data the instant a write occurs to the
virtual disk. 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.

Snapshot Repository Virtual Disk

When you create a snapshot virtual disk, it automatically creates a snapshot repository virtual disk. A snapshot
repository is a virtual disk created in the storage array as a resource for a snapshot virtual disk. A snapshot repository
virtual disk contains snapshot virtual disk metadata and copy-on-write data for a particular snapshot virtual disk. The
repository supports one snapshot only.
You cannot select a snapshot repository virtual disk as a source virtual disk or as a target virtual disk in a virtual disk
copy. If you select a Snapshot 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.
CAUTION: Before using the Snapshot Virtual Disks Premium Feature in a Windows Clustered configuration, you
must map the snapshot virtual disk to the cluster node that owns the source virtual disk. This ensures that the
cluster nodes correctly recognize the snapshot virtual disk.
26