M3 vs Thanos: What are the differences?

Introduction

M3 and Thanos are both open-source projects that provide scalable and highly available metrics storage for Prometheus. While they serve a similar purpose, there are key differences between the two.

1. Data Sharding: M3 uses consistent hash-based sharding for distributing data across multiple nodes, which allows for higher scalability and efficient storage utilization. In contrast, Thanos uses a more traditional approach of store-level sharding, where data is stored in individual blocks and may result in uneven utilization of resources.

2. Multi-Tenancy: M3 natively supports multi-tenancy, allowing for easy isolation and management of metrics from different users or applications in a single M3 cluster. Thanos, on the other hand, does not provide built-in multi-tenancy, although it can be achieved through external tools or configurations.

3. Query Language Compatibility: M3 supports a superset of Prometheus' PromQL query language, which includes additional functions and optimizations. Thanos, on the other hand, provides full compatibility with PromQL as it relies on Prometheus for query processing.

4. Data Consistency: M3 guarantees strong consistency for write operations across its distributed nodes through a distributed consensus algorithm. Thanos, on the other hand, provides eventual consistency for replicated data, which may introduce some lag in data availability after writes.

5. Data Availability: M3 ensures high availability of data by replicating it across multiple nodes, ensuring that data is accessible even in the event of individual node failures. Thanos, on the other hand, relies on Prometheus federation to achieve data availability, where each Prometheus instance stores a subset of metrics and Thanos aggregates data from multiple instances.

6. Storage Backend: M3 supports various storage backends, including local disk, cloud object storage, and distributed file systems like HDFS. Thanos primarily relies on cloud object storage for long-term storage, specifically targeting integration with providers like AWS S3 or Google Cloud Storage.

In Summary, M3 provides consistent hash-based sharding, multi-tenancy support, and an extended query language, while Thanos relies on store-level sharding, lacks native multi-tenancy, and offers full compatibility with PromQL. M3 guarantees strong consistency, replicates data for high availability, and supports multiple storage backends, while Thanos provides eventual consistency, relies on Prometheus federation, and primarily utilizes cloud object storage for long-term retention.