Reference Guide

Table 2. Deployment prerequisites for stretched clusters (continued)
Component Requirements
● If two sites have host networks in different subnets, no
additional configuration is needed for creating clusters.
Otherwise, manual configuration of the cluster fault
domain is required.
● RDMA Adapters for Storage/SMB traffic.
● RDMA is not supported for Replica traffic across WAN.
● At least a 1 Gb network between sites for Replication and
inter-site Live Migration is required.
● The bandwidth between sites should be sufficient to meet
the write I/Os on the primary site.
●
An average latency of 5 ms or lesser for Synchronous
Replication.
● There are no latency requirements or recommendations for
Asynchronous replication.
● There is no recommendation from Microsoft regarding
the maximum distance between sites that a stretched
cluster can support. Longer distances normally translate
into higher network latency.
Windows Admin Center Node Windows features required:
RSAT-Clustering
RSAT-Storage-Replica
Number of nodes supported
Minimum: 4 (2 Nodes per site)
Maximum: 16 (8 Nodes Per Site)
Number of drives supported Minimum of 4 drives per node. Both sites should have
the same capacity and number of drives. Dell Technologies
currently supports only an All-Flash configuration for
stretched clusters.
Tuning of cluster heartbeats
(get-cluster).SameSubnetThreshold = 10
(get-cluster).CrossSubnetThreshold = 20
SDN/VM Network SDN on multi-site clusters is not supported at this time.
For the maximum supported hardware configuration, see Review maximum supported hardware specifications.
Customer network team requirements
Depending on the network configuration chosen, customers should ensure that the requisite end-to-end routing is enabled for
inter-site communication. A minimum of one IP route or three IP routes based on Basic or High Throughput configuration is
required for the environment.
Depending on the network configuration, the customer network team may also need to add static routes on the switches or on
Layer-3 to ensure site-to-site connectivity.
Design principles and best practices
Stretched clusters and Storage Replica
A stretched cluster setup has two sites and two storage pools. Replicating data across WAN and writes on both sites results
in lower performance compared to a standalone Storage Spaces Direct Cluster. Low latency inter-site links are necessary for
Solution deployment
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