Virtual Machines on Google Cloud Platform

Preemptible Virtual Machine : Affordable compute instances suitable for batch jobs and fault-tolerant workloads.

Overview : Preemptible VMs are designed to be a low-cost, short time duration option for batch jobs and fault-tolerant workloads. These VMs offer the same machine types and options as regular compute instances and last for up to 24 hours. Google is offering extra capacity at a discount with the tradeoff - if the same capacity is needed for other resources -  instances can be terminated or “preempted”. If your applications require batch processing, using preempted VM’s will slow down your job without completely stopping it. Also, if your applications are fault tolerant and can withstand possible instance preemptions, then according to Google, preemptible instances can reduce your Compute Engine costs by up to 80%.

Uses : A Preemptible VM can be used for applications or systems that distribute processes across multiple instances in a cluster. While a termination would be disruptive for common enterprise applications, such as databases, it is hardly noticeable in distributed systems that run across clusters of machines and are designed to tolerate failures. Prospect most likely to use Preemptible VMs tend to work in web development, software development, emerging technology research and development, big data and analytics, continuous integration/continuous delivery (CI/CD), and testing.

Cost : Pricing for preemptible VMs is fixed, so you know in advance what you will pay. You can view the preemptible price alongside the on demand prices in Google’s compute pricing list or Google pricing calculator. Prices are 70-80% off on demand, and upto around 50% off even compared to a 3-year committed use discount. 

Google will not charge you for instances if they are preempted in the first minute after they start running. Google Cloud Free Tier credits for Compute Engine do not apply to preemptible instances. 

Shielded Virtual Machine : Hardened virtual machines on Google Cloud.

Overview : Shielded VMs offer protection against a range of threats that are increasingly common in cloud environments, such as rootkits and bootkits or malicious drivers and guest firmware. Other threats include insider attacks and compromises. Shielded VM instances run firmware which is signed and verified using Google's Certificate Authority, ensuring that the instance's firmware is unmodified and establishing the root of trust for Secure Boot.

Uses : Shielded VMs leverage advanced platform security capabilities to help ensure your VMs have not been tampered with. Using Shielded VMs, you can monitor and react to any changes in the VM baseline as well as its current runtime state.