Administrator Guide

C
cache coherency
Managing the cache so that data is not lost, corrupted, or overwritten. With multiple processors, data blocks may have several
copies, one in the main memory and one in each of the cache memories. Cache coherency propagates the blocks of multiple
users throughout the system in a timely fashion, ensuring that the data blocks do not have inconsistent versions in the different
processors caches.
cluster
Two or more metro node directors forming a single fault-tolerant cluster, deployed as one to four engines.
cluster deployment ID
A numerical cluster identifier, unique within a metro node cluster. By default, metro node clusters have a cluster deployment ID
of 1. For multi-cluster deployments, all but one cluster must be reconfigured to have different cluster deployment IDs.
cluster ID
The identifier for each cluster in a multi-cluster deployment. The ID is assigned during installation.
clustering
Using two or more computers to function together as a single entity. Benefits include fault tolerance and load balancing, which
increases reliability and up time.
cluster IP seed
The metro node IP seed is used to generate the IP addresses used by the internal components of the metro node. For more
information about components and their IP addresses, see the Dell EMC Installation and Setup Guide for metro node. Cluster ID
is used by the virtualization software (inter director messaging, cluster identification).
COM
The intra-cluster communication. The communication used for cache coherency and replication traffic.
command line interface (CLI)
An interface that supports the use of typed commands to execute specific tasks.
consistency group
A metro node structure that groups together virtual volumes and applies the same detach and failover rules to all member
volumes. Consistency groups ensures the common application of a set of properties to the entire group. Create consistency
groups for sets of volumes that require the same I/O behavior in the event of a link failure. There are two types of consistency
groups:
● Synchronous Consistency Groups - Use write-through (synchronous) cache mode to write data to the underlying storage
before an acknowledgment is sent to the host. This is dependent on the latency between clusters and the application's
tolerance of the latency.
● Asynchronous Consistency Groups - Use write-back (asynchronous) cache mode to write protect data by mirroring it to
the memory of another director in the cluster. Data is destaged asynchronously to the back-end storage arrays. Writes are
acknowledged once the data has been committed to disk in write order.
continuity of operations (COOP)
The goal of establishing policies and procedures to be used during an emergency, including the ability to process, store, and
transmit data before and after.
controller
A device that controls the transfer of data to and from a computer and a peripheral device.
D
data sharing
The ability to share access to the same data with multiple servers regardless of time and location.
Glossary
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