Administrator Guide

Synchronous replication use cases
20 Dell EMC SC Series: Synchronous Replication and Live Volume | CML1064
4 Synchronous replication use cases
Replicating data can be a valuable and useful tool, but replication by itself serves no purpose without tying it
to a use case to meet business goals. The following sections highlight sample use cases for synchronous
replication.
4.1 Overview
Array-based replication is typically used to provide upper tier application high availability or disaster recovery,
a data protection process to enable image or file-level backup and recovery, or a development tool to
generate copies of data in near or remote locations for application development or testing purposes. For
many business use cases, asynchronous replication provides a good balance of meeting recovery point
objective (RPO) and recovery time objective (RTO) service level agreements without a cost-prohibitive
infrastructure such as dark fibre, additional networking hardware, or additional storage. This is why
asynchronous replication is often used between data centers where longer distances are involved.
However, there are an increasing number of designs where a strong emphasis is placed on the prevention of
data loss. Regardless of where the need originates, the method of replication that satisfies zero transaction
loss is synchronous. The next few sections highlight examples of synchronous replication with a focus on high
consistency for zero data loss or high availability for relaxed data consistency requirements.
4.2 High consistency
The primary need for synchronous replication is preventing data loss or guaranteeing data consistency
between the source and destination replica volume. Synchronous replication provides the same data
protection benefits for both proactive and reactive use cases. Refer to section 3 for more detail on
synchronous high consistency replication operational characteristics.
4.2.1 VMware and Hyper-V
When virtualized, server workloads in the data center are encapsulated into a small set of files that represent
the virtual BIOS, virtual hardware resources, and the virtual disks that provide read and write access to data.
The I/O profile is dependent on the virtual machine role and the applications and services running within it.
Virtual machines work particularly well with replication because their compute resources are portable and
hardware independent by nature. Their inherent mobility, combined with storage replication, allows them to
easily migrate from one site to another, with comparatively little effort required to bring them online at the
destination site. Virtual machines may be relocated for load balancing or disaster avoidance/recovery
purposes. Whatever the reason for relocation, high consistency synchronous replication will ensure that the
contents of the virtual machine at the source and destination match. In the event the vSphere or Microsoft
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Hyper-V
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virtual machine needs to be migrated to a host or cluster of hosts at the destination site, data
consistency of the virtual machine being brought up at the destination site is guaranteed. Disaster recovery is
covered in more detail in section 4.5.
Note that Dell Storage Manager DR plans cannot be predefined with Live Volumes. Predefined DR plans are
supported with regular (asynchronous or synchronous) volume replications or with a managed (cascaded or
hybrid) asynchronous replication from a Live Volume.