Array-based replication versus vSphere Replication

26 July,2021 by Tom Collins

In large scale migrations DBAs are asked to make decisions with far-reaching and with unforeseen consequences. Deciding which approach to take is influenced by a number of factors including footprint size of inventory , duration of migration window , VMWare protection, application requirements , downtime requirements 

Array-based replication

-replication happens at the storage layer

-replication level: LUN,VMFS or NFS

-Microsoft Cluster Services - MSCS cluster VMs can be replicated 

-Downtime involved , coordination required 

vSphere Replication 

replication level :replicates at the VM level. More flexibility about moving the VMs

uses a different protocol   than array based replication 

downtime is minimal 

MSCS cluster VMs cannot be replicated . vSphere replication cannot replicate disks in multiwriter , I've attempted to use this one previously - but 

Physical RDMs are not supported in vSphere replication 

 

The other common method is vmotion . The advantage of vmotion is minimal to no downtime . The disadvantage of vmotion is there isn't as much as flexibility -  as opposed to vsphere replication

Ideally vMotion in less busy times, random access patterns on virtual disks interfere with sequential access of svMotion , causing negative impact. 

svMotion migrate in 64kb chunks - this may have a negative impact on requests using a smaller size 

Expect increased CPU consumption during svMotion . 

 

 

 

 

 


Author: Tom Collins (http://www.sqlserver-dba.com)


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