In this series of SRM we will see about Site Recovery Manager. In previous post we have looked at the Replication options supported in SRM. In this post we will see on Different Topologies you can use with SRM based on your requirement. Site Recovery Manager supports 5 types of topologies which we will see in detail in this post. Different Topologies help customers to look for the different failover and disaster scenarios which they can get while using SRM. Site Recovery Manager is an disaster recovery solution from VMware to provide availability to your virtual infrastructure at the time of disaster or any failover. Site Recovery Manager is integrated with the vSphere web client so you can easily manage Topologies from single pane.
Below are the Topologies you can configure with SRM:
- Active-Passive
- Active-Active
- Bi-directional
- Stretched Storage
- Multi-Site
So let’s look how each topologies work.
Active-Passive:
This is the most common topology you will find with every disaster recovery solution. Where your one site will work as Active and another site will work as Passive. Below is the simple diagram of
the topology.
This topology you will find most used with any of the disaster recovery solution. In this topology your Protected site also called as DC site runs all your virtual machines, Applications while your Recovery Site also called as DR site which will stay idle every time. Once the Disaster has occurred and you do a recovery your Recovery site becomes the Active site.
Active-Active:
This topology also you will find in DR Solutions where your some of the virtual machines and applications runs Actively from DC site and some run from DR Site. Below is the simple diagram of the topology.
This topology helps customers to run their Test or Dev environments at the recovery site, So you can save more resources at the primary site. This topology you may find used by many customers so they can use their resources at DR site efficiently.
Bi-directional:
As the name suggests you can easily understand this topology works in both the direction. In this topology you will be using both the sites running and replicating your resources at both the sites.
Below is the simple diagram of the topology.
You might already having idea of how this topology works but let’s clear it once again. In Bi-directional topology virtual machines and applications runs on both the sites, That means your both the sites will work as an active site. Your Virtual machines and Applications protected from both sites, means that DC site VMs are protected at DR site and vice versa.
Stretched Storage:
You can easily understand by the name that how this topology works. Your storage is stretched between 2 sites. Below is the simple diagram of the topology. 
Now Site Recovery Manager can take advantage of Stretched storage which was previously only available with vSphere Metro clusters. This topology mainly provide 2 benefits zero-downtime disaster avoidance and Planned maintenance downtime. So now you can use more features of SRM with stretched storage. Now you can easily do the vMotion of the protected virtual machines between sites but there are requirements of Stretched layer 2 network connectivity between site is must. If you want you can also go for NSX which provides an added advantage for networking within hosts.
Multi-Site:
This is an additional recovery solution supported with Site Recovery Manager where you can use and configure multiple sites with SRM. There are 2 types of configurations is supported.
Shared Recovery: Below is the simple diagram of shared recovery supported by SRM. 
In the shared recovery configuration where you have multiple branch offices in place and you want to configure availability for them, that can be achieved using this feature. Where your multiple remote sites are protected by single recovery site. So you don’t have to configure multiple recovery sites.
Shared Protection: Below is the simple diagram of Shared Protection supported by SRM. 
As you can easily understand from the above image that we have 3 sites in working where Site A is protected and can be recovered at Site B, In Second case Site B is protected site and can be recovered at Site C. In Third case Site C can be recovered at Site A. There are some limitation also comes with this type of configuration which are each VM can only be protected by single SRM pair and Failover of a VM can not be done at different or multiple recovery sites. As we have seen multiple topologies supported by Site Recovery Manager which provides the continuous availability and disaster recovery. Now you can make decisions based on your requirement and Infrastructure which topology you would like to go for. Each of the Topology has its own benefits and costs involved.
Checkout Site Recovery Manager Deep Dive for Installation,Configuration and Recovery :
Site Recovery Manager Deep Dive
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Image Credits: VMware. Reference: VMware SRM Technical Overview.
