1. Data Source Integration: Grafana supports a wide range of data sources, including popular databases, cloud monitoring services, and APIs, allowing users to visualize data from various sources. On the other hand, Thanos primarily focuses on integrating with Prometheus, an open-source monitoring and alerting toolkit, extending its capabilities to support high availability, long-term storage, and global querying across multiple Prometheus instances.

2. Scalability: Grafana is suitable for small to medium-sized deployments, providing a user-friendly interface with easy setup and configuration. In contrast, Thanos is designed for large-scale deployments, enabling horizontal scalability with federation and global querying capabilities. It allows users to seamlessly scale their monitoring infrastructure as their needs grow.

3. Data Retention and Long Term Storage: Grafana offers flexible data retention options, allowing users to choose how long data is stored, which can be adjusted according to their needs. On the other hand, Thanos excels in long-term storage and retention by providing a highly scalable and distributed storage system. It enables efficient querying of historical data, even when Prometheus instances are no longer available.

4. High Availability: Grafana supports high availability setups, allowing users to configure multiple instances for redundancy and fault tolerance. However, achieving high availability in Grafana requires additional setup and configuration. Meanwhile, Thanos inherently provides high availability through its federation feature. It allows users to federate multiple Prometheus instances and query them as a single logical entity, providing fault tolerance and resilience out of the box.

5. Global Querying: While Grafana offers powerful querying capabilities, it is limited to querying data from a single data source at a time. Thanos, on the other hand, allows users to perform global querying across multiple Prometheus instances. This means users can query and analyze data from multiple sources simultaneously, enabling cross-data source analysis and correlation.

6. Alerting and Monitoring: Grafana provides built-in alerting and monitoring capabilities, allowing users to set up alerts based on various conditions and receive notifications when certain thresholds are met. Thanos, being an extension of Prometheus, inherits its alerting and monitoring functionality. It maintains Prometheus's rule and alert manager, providing a reliable and robust alerting system.

In Summary, Grafana offers a user-friendly interface with broad data source integration and flexible data retention options, making it suitable for small to medium-sized deployments. On the other hand, Thanos specializes in scalability, long-term storage, high availability, global querying, and alerting for large-scale deployments.