preparing
In a Global Mirror relationship, the state that occurs when any changed
write data for the source virtual disk (VDisk) is flushed from the cache.
Any read or write data for the target VDisk is discarded from the cache.
primary virtual disk
In a Metro or Global Mirror relationship, the target of write operations
issued by the host application.
property
In the Common Information Model (CIM), an attribute that is used to
characterize instances of a class.
PuTTY
A client program that allows you to run remote sessions on your computer
through specific network protocols, such as SSH, Telnet, and Rlogin.
Q
qualifier
A value that provides additional information about a class, association,
indication, method, method parameter, instance, property, or reference.
quorum
A set of nodes that operates as a cluster. Each node has a connection to
every other node in the cluster. If a connection failure causes the cluster to
split into two or more groups of nodes that have full connection within the
group, the quorum is the group that is selected to operate as the cluster.
Typically, this is the larger group of nodes, but the quorum disk serves as a
tiebreaker if the groups are the same size.
queue depth
The number of I/O operations that can be run in parallel on a device.
quorum disk
A managed disk (MDisk) that contains a reserved area that is used
exclusively for cluster management. The quorum disk is accessed in the
event that it is necessary to determine which half of the cluster continues
to read and write data.
quorum index
The pointer that indicates the order used to resolve a tie. Nodes attempt to
lock the first quorum disk (index 0), followed by the next disk (index 1),
and finally the last disk (index 2). The tie is broken by the node that locks
them first.
R
rack A free-standing framework that holds the devices and card enclosure.
RAID See redundant array of independent disks.
RAID 0
IBM definition: RAID 0 allows a number of disk drives to be combined
and presented as one large disk. RAID 0 does not provide any data
redundancy. If one drive fails, all data is lost.
HP definition: A RAID storageset that stripes data across an array of disk
drives. A single logical disk spans multiple physical disks, allowing
parallel data processing for increased I/O performance. While the
Glossary 177
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