You are tasked with deploying a stateful workload on Google Cloud Platform. This workload must be scalable horizontally, meaning it can add or remove instances as needed based on load. Each instance in this workload requires the ability to read and write to the same POSIX-compliant filesystem, and during peak load, the system must handle up to 100 MB/s of writes. Considering these requirements, what is the most appropriate storage solution you should implement?