GlobalTech has a legacy application that requires a shared, POSIX-compliant file system that multiple Compute Engine VMs need to mount and access…

Cloud Filestore is Google Cloud's fully managed Network Attached Storage (NAS) service. It provides a Network File System (NFS) that is POSIX-compliant, which is a core requirement of the question. Filestore instances can be mounted as a shared file system by multiple Compute Engine VMs concurrently, making it the ideal solution for sharing configuration files and temporary data among legacy applications that expect a traditional file system interface. It is a managed service, abstracting away the complexity of managing a file server.

A. Cloud Storage is an object store, not a POSIX-compliant file system. While it can be mounted with gcsfuse, it has semantic differences and performance limitations compared to a true POSIX file system.

B. Cloud Bigtable is a NoSQL wide-column database. It is designed for large-scale analytical and operational workloads and does not provide a file system interface that can be mounted by VMs.

C. Cloud SQL is a managed relational database service. Storing files as BLOBs in a database is inefficient for this use case and does not offer a mountable, POSIX-compliant file system.

1. Google Cloud Documentation, Cloud Filestore Overview: "Cloud Filestore is a managed file storage service for applications that require a filesystem interface and a shared filesystem for data. Filestore gives users a simple, native experience for standing up managed Network Attached Storage (NAS) with their Google Compute Engine and Kubernetes Engine instances." (Source: https://cloud.google.com/filestore/docs/overview, Section: "What is Cloud Filestore?")

2. Google Cloud Documentation, Comparing Cloud Storage and Filestore: "Filestore is a good option for workloads that require operating system-level file access to shared data... Filestore is fully POSIX-compliant and has shared access for files." (Source: https://cloud.google.com/filestore/docs/comparison-with-other-storage-options, Section: "When to use Filestore")

3. Google Cloud Documentation, Cloud Storage FUSE: "Cloud Storage FUSE is not a POSIX-compliant file system... There are semantic differences between Cloud Storage FUSE and a traditional file system." (Source: https://cloud.google.com/storage/docs/gcs-fuse, Section: "Semantics")

4. Google Cloud Documentation, Cloud Bigtable Overview: "Cloud Bigtable is a sparsely populated table that can scale to billions of rows and thousands of columns... It is ideal for applications with high-throughput data ingestion or analytics." (Source: https://cloud.google.com/bigtable/docs/overview, Section: "What Cloud Bigtable is good for")