Thursday, June 6, 2013

Demystifying vSphere Replication


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******                 Updated information - Dec 11, 2013            ******
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 vSphere Replication is a replication engine feature provided by VMware that allows data replication from one storage to another, since it does not depend on array base replication technology, you can use it to replicate data between storages from different vendors even using host’s local datastore.



Since the release of vSphere 5.1, this feature is built-in on the majority of the vCenter’s licese, just vSphere Essentials does not contain this feature.
So it’s a lot less expensive solution for data replication. It’s FREE, indeed.

To eliminate any doubt that might exist, these data replicated are the virtual machines disks (VMDK).

The companies are using it on several ways.
- Building disaster recovery site.
- Migration from datastores.
- Migration to new datacenters.
- Creating a backup copy of a VM.

You might remember that starting with SRM5.0, vSphere Replication was part of it and it still there.

That’s when the things get a little confusing.

Checking vSphere ReplicationAdministration Guide, you will notice, under the limits section, the following statement:

You can only deploy one vSphere Replication appliance on a vCenter Server instance. Deploying more than one vSphere Replication appliance is not prohibited, but might lead to unexpected results.

While checking SRM installation and configuration Guide, you will notice, over and over through the document, the following statement,:

If necessary, you can deploy multiple vSphere Replication servers to balance the replication load across your virtual infrastructure.
To meet the load balancing needs of your environment, you might need to deploy additional
vSphere Replication servers at each site.

Very confusing , right ?
Can I or Cannot I deploy multiple vSphere Replication Servers ?

I believe part of that misunderstanding is a lack of identification of product’s names, Even dough the feature is the same, the product itself changes, depending where you deploy it from.
From now on, I will call the vSphere Replication that you deploy direct on the vCenter, without the SRM, as vSphere Replication Stand Alone and the one you deploy through SRM the Embedded vSphere Replication.
Let’s go to the differences:
vSphere Replication Stand Alone: You can deploy just ONE on each vCenter instance and it will allows you to handle at a maximum of 500 VMs.
 Embedded vSphere Replication: You can deploy up to 10 vSphere Replication Servers (always through SRM interface), while the maximum of VMs replicated still at 500 VMs, in this case, each vSphere Replication can handle at a maximum of 100 VMs. So, to support 500 VMs replicated you would need to deploy 5 Embedded vSphere Replication servers.
What if I already have vSphere Replication Stand Alone installed and replicating VMs and then install SRM ?
SRM will recognize the VMs replicated and will use them as base for protection groups and recovery plans, but the Stand Alone limits will need to be respected. If you want to deploy more vSphere Replication Servers, uninstall the Stand Alone version and start deploying the new ones from SRM, in this situation the limits are the ones from Embedded vSphere Replication.
A little clear now ?

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I’m and IT specialist with over 15 years of experience, working from IT infraestructure to management products, troubleshooting and project management skills from medium to large environments. Nowadays I'm working for VMware as a Senior Consultant, helping customers to embrace the Cloud Era and make them succefully on this journay. Despite the fact I'm a VMware employee these postings reflect my own opnion and do not represents VMware's position, strategies or opinios.

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