Last Update: Sep 04, 2024 | Published: Nov 04, 2016
This post will show you Microsoft’s method for calculating the storage account requirements and replication bandwidth requirements for the DR-in-the-cloud solution, Azure Site Recovery (ASR), for VMware and Hyper-V.
I’ve been asked “How much bandwidth do I need for ASR?” countless times. How long is a piece of string? The bandwidth requirements of any kind of replication system are dependent on several factors; I’ll break these into two phases:
Luckily, ASR uses asynchronous replication, so latency is not an issue. You might choose to use a local Azure region for your recovery services vault(s), or you might opt to use a remote region for an additional layer of protection.
Storage is the second variable. Everyone realizes that the amount of storage required impacts the cost of the solution, but few ever thing about storage account performance. ASR supports Standard Storage (HDD) and Premium Storage (SSD) accounts. The other issue is that a storage account has a limit on performance, so you might need to have multiple storage accounts instead of just one. How will you know how many you need, short of sticking a wet finger in the air?
Microsoft has shared a process that allows us to scientifically estimate our bandwidth and Azure requirements for an ASR deployment. The process works as follows:
We need to identify the machines in the on-premises environment, get disk size information, and determine data churn. Both Microsoft and VMware share tools for doing so for their respective hypervisors:
You should run those tools for as long as you can to get a realistic scan of your environment. Then you can use the resulting information to size ASR.
The ASR Capacity Planner is a spreadsheet tool that you can use, assuming you have gathered the required data, to size your ASR deployment. The tool works in two ways:
The Quick Planner is easy to use. You enter:
You get results instantly — note that the bandwidth requirements are for ASR, in addition to whatever other services your business is running:
Alternatively, if you have detailed per-machine data, you can use the detailed planner. This approach will take more time, but the results will be more accurate.