Microsoft has finally released the Azure Site Recovery (ASR) Planner to help you understand, design, and size your disaster recovery (DR) solutions in Azure for on-premises VMware and Hyper-V deployments.
The process of enabling replication of a virtual machine to Azure is very simple. It’s actually the first hands-on lab that my students do when I reach ASR. What is more complicated is understanding what is already deployed, determining what to deploy in Azure, and sizing the bandwidth requirements.
Ah! The ever-present question with the cloud, “How much bandwidth do I need?” In the case of ASR or any DR solution/service, the only answer is, “You need as much as you require.” Few are ever happy with that answer, as you might imagine. The bandwidth requirements break down as follows:
- Initial Sync: The initial sync is when you use the most bandwidth; you will gradually add virtual machines to the ASR service and each VM will completely copy its disks to the cloud.
- Replication: Each virtual machine transitions from initial sync to replication after the initial sync is finished. VMware and physical machines use continuous asynchronous replication and Hyper-V virtual machines use interval-based asynchronous replication based on a policy that you define (every 30 seconds, 5, or 15 minutes) and associate with virtual machines.
The initial sync will probably take a long time to complete, from machine 1 all the way to the last machine. How long is a matter of how much data you need to copy versus how much bandwidth you have available. On a long-term basis, your bandwidth requirements are dictated by data churn; changes must be replicated soon after (asynchronous replication) the changes are committed to on-premises storage.
Up until now, we didn’t have great tooling to estimate bandwidth requirements or other requirements such as storage accounts (tier and performance). A spreadsheet-based tool called the Azure Site Recovery Capacity Planner could take information from other Hyper-V/VMware monitoring tools but that required a lot of manual effort. I’m not aware of any of my customers using the tools.
On March 1st, Microsoft launched a preview for a new tool that supported VMware only, the ASR Deployment Planner for VMware. This was a tool that would scan/monitor our on-premises environment and produce a report that would size and help plan the DR site. Now we had something we needed … sort of. A Hyper-V release was supposed to come soon after … and it didn’t. Ignite (end of September) came and went too. But in December, Microsoft made the tool generally available with support for VMware and Hyper-V.
What the ASR Deployment Planner Does
The ASR Deployment planner connects to your hosts to gather data. Note that nothing is installed in the virtual machines and no ASR components need to be deployed. The data that is gathered allows the tool to produce a report with a lot of information and recommendations, including:
- Compatibility: Is the virtual machine configuration and guest OS compatible with Azure and ASR?
- Bandwidth: How much bandwidth is required for replication and how does this bandwidth impact your desired recovery point objective (RPO – how much data is lost after failover).
- Azure infrastructure requirements: The quantity and tier of storage accounts that are required to maintain the required performance of failed over virtual machines. You are also given guidance on the required number of cores (subscription limits) and virtual machine series/sizes (optionally configured after the initial synchronization is complete).
- On-premises infrastructure requirements: Hyper-V replication is based on Hyper-V Replica, which consumes storage for Hyper-V Replica Log (HRL) files. VMware customers will get guidance on the configuration/process server requirements.
- Initial Synchronization: The more machines you add to replication at once, the worse the bandwidth is hit. The tool will make recommendations on batch size versus available bandwidth.
- Cost analysis: An estimate of your Azure costs will be produced.
The addition of this tool should make it a little easier to plan ASR deployments but you will still need to have a good understanding of:
- What to replicate versus what not to replicate and what must be deployed with application layer replication over site-to-site network connections (see Active Directory)
- What you must pre-deploy in the DR virtual network
- What you must pre-deploy in any sandbox test failover virtual networks