Reliability engineering for SAP on Azure

The business demands of today drive organizations to develop a strategy to migrate SAP apps to the cloud. There are obvious advantages for businesses that make the choice to move to cloud computing – costs, much greater access, pay-as-you-go usage, the ability to scale up & down as appropriate and security & backup, to name a few. This blog talks about the components involved in designing the SAP landscape in Azure Cloud.

Availability requirement is one of the key considerations when designing the application. This determines the minimum guaranteed availability of the application or in other words how long the business can hold a downtime period. These are determined by the criticality of the application and impact on the overall business. Before diving deep in looking at setting up cluster components, we need to understand what cloud service provider can offer from availability perspective for the underlying infra and its components.

It is a better practice to consider this and designing the landscape, thus will help us to plan better for requirement. It spares time and costs if the underlying cloud provider fulfills the requirements automatically. Having said that, let us explore how critical components involved in designing the SAP landscape can be made accessible in the Azure Cloud.

 

 

Some of the key Azure components in the SAP landscape :

  • Virtual Machine
  • Managed disks
  • Azure storage account
  • Express route & VPN gateway
  • Azure firewall

Virtual Machine

The Virtual Machine that have two or more instances deployed across two or more availability zone in the same region will have atleast 99.99% of uptime. These are typically leveraged by a production landscape, where more than one SAP application server and DB server (primary / secondary) are deployed to ensure higher availability. The advantage of this, we will have access even if a whole availability zone goes down. Note, this up time is for VM only, as a client owns the application, the underlying implementation is not component of the SLA. This is a cost-effective, default solution to attain increased uptime and costly complex cluster solutions with no extra expenditures.

We have to leverage cluster solutions such as pacemakers or another 3rd party solution, NFS with DRBD for storage, native DB replication and Azure load balancer to obtain the high availability at SAP application level. For single instance virtual machine the guaranteed uptime is at least 99.9 provided the application uses premium storage for all OS and data disks.

This is typically the case with the SAP system, in which the DB and application servers run on the same VM or a system which has only one application and DB server. Again, only the OS portion of it is covered. With a 99.9 per cent uptime, non-productive system offers an excellent system availability, usually this a favourable uptime SLA for production instance for some customer.

One must therefore take into account both the accessibility at application level and VM level, in order to meet the underlying business requirement.

Managed Disk

Azure managed disk does not have the SLA on its own ; it uses the underlying  VM and uptime guarantees for the storage account.

Azure Storage Account

In general, Azure offers read and write uptime separately. Azure provides 99.99% of successful read time for Read Access-Geo Redundant Storage (RA-GRS) storage accounts. 99.9% for Locally Redundant Storage (LRS), Zone Redundant Storage (ZRS), and Geo Redundant Storage (GRS) Accounts.

Azure provides 99.9% of successful write data in the accounts for Locally Redundant Storage (LRS), Zone Redundant Storage (ZRS), and Geo Redundant Storage (GRS) Accounts and Read Access-Geo Redundant Storage (RA-GRS) Accounts.

Azure Firewall

As for Azure Firewall the minimum uptime is around 99.95%.

Azure Firewall offers fully stateful native firewall capabilities for Virtual Network resources, with built-in high availability and the ability to scale automatically.

Azure Firewall guarantees at least 99.99% when deployed within two or more availability zones in the same Azure region and at least 99.95% availability, when deployed within a single availability zone.

ExpressRoute & VPN gateway

With respect to express route Azure provides a minimum of 99.95% of uptime. For VPN gateway 99.9% for basic Gateway for VPN or for ExpressRoute and 99.95% for all other gateway excluding basic.When architecting landscape for customer we puzzled the requirement with Azure inbuilt availability and along with other components like pacemaker cluster, NFS cluster, Stonith, etc to achieve the requirement to arrive at the final solution.

Our goal is to assist companies make the most of SAP migration to Azure and work with them to produce the best of cloud and SAP solutions that support tangible business outcomes. Read further our case-studies about SAP on Azure platform for further insights.

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