Spot Virtual Machines- An insight
Azure Spot Virtual Machines are the Virtual machines (VM) which are unused with the platform having spare compute capacity. So, anyone with an extra workload and in need of added capacity can take advantage of this Azure feature at a very low cost or a significantly discounted rate, in contrast to the Pay-As-You-Go pricing structure. Azure has a lot of cloud servers set aside and the clientele doesn’t get to use that inventory enough. So these VMs are rented out to them and are called Spot Virtual machines.
A win-win situation for both parties, this alternative sometimes allows Azure cloud customers to receive up to 90% discount and thus appreciably reduce their computing costs. When demand for VMs or compute capacity is too high, Azure can regain possession of the servers, shortly after a small warning. So, this feature is not suitable for tasks that require limited interruptions.
The company allocates VMs according to availability of capacity. The amount of surplus compute capacity of the servers may vary with respect to time of the day, size of the VM and location of VM deployment etc.
Applications of Spot Virtual Machines
For high performance
A task that requires several CPU or GPU based computers to deal with complex mathematical algorithms is a case in point. Here the Azure Spot VM pricing structure is perfectly suitable due to its ideal blend of performance and price. Since these kinds of tasks take time and users are patient, being aware that calculations linger on, no amount of interruption impacts the user experience.
Azure Spot VMs are conducive to batch processing jobs too. These jobs or assignments follow a similar path where a programme allots a task to a computing system for execution. If these are time consuming batch processing jobs, then getting them done through Spot VMs is a very economical option.
Since there is no interchange of data while the batch processing job is being performed a disruption or breach will not affect the experience of a user.
Development /Test cases
The development or test environment is another appropriate use case for Azure Spot VMs. Customarily, these settings do not need high availability of VM compute capacities. These scenarios are barely significant with respect to IT funds.
The location for these unpopular and less important services is generally the legacy of on-premises hardware. However, an Azure environment and a legacy on-premises hardware do not blend properly. This combination also brings about unnecessary complications when there is a requirement of involving fixes or releases in a DevOps scenario. Therefore, leveraging Spot VMs is the right move.
When Spot price becomes more than the maximum price or should Microsoft need its VMs back, the company grants a notice of 30 seconds. There are two eviction methods as per capacity and the maximum price, set during the configuration phase.
1- Capacity only
For pay-as-you-go workloads, when Azure requires capacity back, it evicts VM. This is due to the fact that the current price of a regular VM is the maximum price for the Spot VM.
2- Price or capacity
In this case, the clients have the option to set the maximum price that they intend to pay for the VM. If Spot price exceeds maximum price or if Azure needs to repossess the capacity for pay-as-you-go assignments then the VMs are evicted.
There are two Eviction policies.
1.Stop/Deallocate – Post eviction of VM, this policy shifts the spot VM to deallocated state but the VM can be reallocated, and the disks can be accessed. However, the storage of the disks of the VM is chargeable.
2.Delete – In this instance, the VM is deleted together with its disks after the eviction. Consequently, charges do not apply.
Azure Spot Virtual Machines offer impressive discounts for unutilized compute capacity. Purchasing either individual Spot VMs or Scale sets helps to reduce cloud spending to a great extent. That being said, proper insights are absolutely essential to make sure that Azure Spot VMs are used suitably and appropriately.