Introduction

As data storage demands continue to grow exponentially, organizations require scalable, reliable, and high-performance storage solutions. Ceph has emerged as a leading open-source distributed storage system designed to meet these needs. At the heart of Ceph’s robustness and efficiency lies the CRUSH (Controlled Replication Under Scalable Hashing) algorithm and its CRUSH maps.

This article explores CRUSH maps, their role in Ceph, and how Micron21 leverages this technology in our mCloud platform to deliver unparalleled storage solutions.

What is Ceph?

Before diving into CRUSH maps, it’s important to understand Ceph’s architecture. Ceph is a unified, distributed storage system offering:
✔ Object Storage
✔ Block Storage
✔ File Storage

By combining these storage types into a single platform, Ceph provides exceptional performance, scalability, and reliability for modern storage needs.

The Role of CRUSH in Ceph

Introduction to CRUSH

CRUSH (Controlled Replication Under Scalable Hashing) is the data placement algorithm that determines how Ceph stores and retrieves data across a cluster. Unlike traditional storage systems that rely on centralized lookup tables, CRUSH enables Ceph to function without bottlenecks, ensuring massive scalability and fault tolerance.

Why CRUSH Matters

✔ Scalability: Eliminates the need for a central directory by calculating data placement on-the-fly, allowing the system to scale to exabyte levels without performance degradation.
✔ Performance: Distributes data evenly and predictably, balancing workloads and optimizing resource utilization.
✔ Reliability: Enhances fault tolerance and data durability through intelligent data placement.

Understanding CRUSH Maps

A CRUSH map is a hierarchical, rule-based representation of a Ceph cluster’s topology and storage policies. It acts as a guide for the CRUSH algorithm, determining where data is stored within the cluster.

Components of a CRUSH Map

✔ Devices: The actual storage drives (HDDs, SSDs, NVMe) where data is stored.
✔ Buckets: Logical groupings of devices or other buckets, which can represent:

• OSDs (Object Storage Daemons): Individual storage devices managed by Ceph.

• Hosts: Physical servers containing OSDs.

• Racks: Groupings of hosts.

• Rows, Pods, Rooms, Data Centers: Higher-level groupings representing the physical layout.
  ✔ Hierarchy: The CRUSH map defines a structured topology of buckets reflecting the physical or logical organization of the cluster.
  ✔ CRUSH Rules: Rules dictating how data is replicated and distributed based on the defined hierarchy.

How CRUSH Maps Work

Data Placement Calculation

When data is written to a Ceph cluster, the CRUSH algorithm consults the CRUSH map to calculate which OSDs should store the data. This eliminates centralized bottlenecks, ensuring efficient data distribution.

Replication Policies

CRUSH rules determine:

• Number of data copies stored (e.g., 3N replication).

• Failure domains to consider (e.g., host, rack, or data center).

Failure Domains

CRUSH ensures data replicas are stored across different failure domains, enhancing resilience and availability. For example, with a 3N replication strategy, data copies are distributed across:
✔ Micron21 Kilsyth Data Centre (Primary)
✔ Melbourne CBD Data Centre (Secondary)
✔ Port Melbourne Data Centre (Tertiary)

This ensures that even in the event of a node or data center failure, data remains accessible and intact.

How Micron21 Utilizes CRUSH Maps in mCloud

Micron21 leverages Ceph’s CRUSH maps to enhance mCloud’s storage performance, scalability, and fault tolerance. Key benefits include:
✔ Optimized Data Placement: Ensures workloads are evenly distributed, preventing hotspots and maximizing performance.
✔ Seamless Scalability: New storage nodes can be added to the cluster without disrupting existing operations.
✔ High Availability & Redundancy: Data remains accessible even during hardware failures or maintenance periods.
✔ Geographically Redundant Storage: With multiple data centers, CRUSH maps ensure that data remains protected against regional failures.

Conclusion

CRUSH maps are the foundation of Ceph’s scalability, efficiency, and reliability. By eliminating the need for a central metadata lookup, Ceph’s CRUSH algorithm allows Micron21’s mCloud platform to provide high-performance, highly available, and resilient storage solutions.

Through intelligent data placement, failure domain awareness, and seamless scalability, Micron21 ensures that businesses relying on mCloud storage experience the highest levels of data durability, availability, and performance.

For more information on how Micron21’s Ceph-based mCloud storage solutions can benefit your business, contact our team today.