HP P6000 Cluster Extension Software Administrator Guide (5697-2274, November 2012)

Disk failure protection occurs when the storage system sets aside reserved capacity to take over
the functionality of a failed or failing physical disk drive. In groups with mixed capacity drives,
the reserved capacity is based on the largest disk in the disk group. The system must cover a
failure in any drive, so it reserves enough capacity to cover the largest failure that could happen.
disk group A named group of disks selected from all the available disks in a disk array. One or more virtual
disks can be created from a disk group. Also refers to the physical disk locations associated with
a parity group.
DLL Dynamic-link library.
DR Data replication.
DR group A logical group of virtual disks in a remote replication relationship with a corresponding group
on another array.
DR group direction The replication direction of a DR group. There are two states:
• Original (from Home)
• Reversed (failed over, or toward Home)
DR group log state The current behavior of the log associated with a DR group. In the state options, references to
multiple destinations are for future use. There are three possible states:
• Normal – No destination is logging or merging.
• Logging – At least one destination is logging; none are merging.
• Merging – At least one destination is merging.
DR group write
mode
Characterizes how a write from a host is replicated. A DR group has two modes of replication
writes from the source vdisk to the destination vdisk:
• Synchronous replication—I/O requests to both source and destination must be complete
before the storage system processes the next I/O request from the host.
• Asynchronous replication—The storage system processes the next I/O request on the source
even if there are outstanding I/O requests on the destination. This mode is not available at
this time.
DR mode The operational mode of a DR group that indicates the capability of I/O to be written to its source
and/or its destination.
DSM Device Specific Module.
dual fabric Two independent fabrics providing multipath connections between Fibre Channel end devices.
DWDM Dense wavelength division multiplexing. The technique of placing many optical signals on a
single optical cable simultaneously.
See also WDM.
enhanced
asynchronous
mode
A write mode in which all host write I/Os are added to the write history log. The controller then
acknowledges that data has been written at the source before being copied at the destination.
Enterprise Virtual
Array (EVA)
An HP storage product that consists of one or more virtual arrays. See also virtual arrays.
fabric A network of Fibre Channel switches or hubs and other devices.
failover An operation that reverses replication direction so that the destination becomes the source and
the source becomes the destination. Failover operations can be planned or unplanned and can
occur between DR groups, managed sets, fabrics or paths, and array controllers.
failsafe mode A DR group mode in which all source vdisks in the group become both unreadable and unwritable
if any of their corresponding destination vdisks is unreachable. No logging takes place for the
vdisks. There are two states:
• Enabled
• Disabled
FC Fibre Channel. A network technology primarily used for storage networks.
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