Comprehensive Ceph Hardware Recommendations for Optimal Performance and Scalability

Introduction

Deploying a Ceph cluster is not just about installing the software—it’s about building a robust foundation to ensure performance, scalability, and reliability. Whether you're aiming for block storage (RBD), object storage (RGW), or CephFS, your hardware choices will play a pivotal role. This guide outlines the best practices for selecting hardware for your Ceph cluster, ensuring the right balance between performance and cost.

Key Factors to Consider When Designing Ceph Hardware

Before diving into hardware specifications, it’s crucial to define your workload and performance expectations:

1. What is the primary use case? Block storage (RBD) for virtual machines and databases. Object storage (RGW) for high-capacity, low-cost storage.
2. File system (CephFS) for large-scale file storage with metadata management.

1. What are your performance goals? Determine if your focus is on low-latency, high IOPS, or maximizing storage capacity.
2. What is your budget? Cost plays a significant role in choosing between HDD, SSD, and NVMe storage.

Recommended Specifications

The following table summarizes the recommended hardware specifications for different Ceph components:

Component CPU Memory Storage Network Monitor Nodes (MON) 4–8 cores 16–32 GB SSD/NVMe (500 GB–1 TB) 10–25 Gbps (dual NICs) OSD Nodes 2–4 cores per OSD 4 GB per TB of storage (16–256 GB per node) NVMe for journals/WAL, HDD for capacity 10–25 Gbps Metadata Servers (MDS) 8–16 cores 64–128 GB NVMe for metadata storage 25 Gbps or higher Client Nodes (CephFS) 4–8 cores 16–32 GB SSD or NVMe (optional) 10–25 Gbps Ceph Managers (MGR) 4–8 cores 16–32 GB SSD for monitoring and logs 10–25 Gbps RGW (Object Gateway) 8–12 cores 32–64 GB SSD for cache, HDD for capacity 25 Gbps or higher

Hardware Selection by Component

1. Monitor Nodes (MON)

Monitor nodes maintain cluster health and state. Stability and reliability are essential for these nodes.

Specifications:

• CPU: 4–8 cores
• Memory: Minimum 16 GB (32 GB recommended for larger clusters)
• Storage: SSD or NVMe (500 GB–1 TB) for fast metadata access
• Network: Minimum 10 Gbps (preferably 25 Gbps for redundancy)

Best Practice: Deploy an odd number of monitors (3, 5, or 7) to ensure quorum and high availability.

2. Object Storage Daemons (OSD)

OSD nodes are the backbone of a Ceph cluster. They store data and handle replication, making them the most performance-critical component.

Specifications:

• CPU: 2–4 cores per OSD daemon
• Memory: 4 GB per TB of storage (16–256 GB per node)
• Storage: NVMe or SSD for journals and RocksDB/WAL (recommended for all setups) HDD (SAS/SATA) for capacity

Storage Configuration Tips:

• Use all-NVMe setups for high-performance block storage.
• For cost-effective solutions, combine HDDs for data with NVMe for journals.
• Avoid RAID for OSD data disks; let Ceph handle replication and redundancy.

3. Metadata Servers (MDS) for CephFS

CephFS requires dedicated metadata servers (MDS) to manage file metadata. These nodes play a critical role in ensuring file system performance.

Specifications:

• CPU: 8–16 cores
• Memory: 64–128 GB
• Storage: NVMe for metadata storage
• Network: 25 Gbps or higher

Best Practice: Deploy multiple MDS nodes for high availability in production environments.

4. Networking Recommendations

A reliable, high-bandwidth network is essential for Ceph performance. The network design can make or break your cluster’s scalability and efficiency.

Network Recommendations:

• Bandwidth: 10 Gbps for small clusters 25 Gbps or higher for production-grade deployments
• Redundancy: Use dual network interfaces with bonding (LACP).
• Jumbo Frames: Enable MTU 9000 for better network performance.

Tip: Separate public and cluster networks to reduce congestion and improve reliability.

Example Configurations

Small-Scale Cluster (Testing and Development)

Component Quantity Specification Monitor Nodes 3 16 GB RAM, SSD, 10 Gbps OSD Nodes 3 4 OSDs per node, 64 GB RAM, 10 Gbps Storage Mixed SSD and HDD setup

Medium-Scale Production Cluster

Component Quantity Specification Monitor Nodes 5 32 GB RAM, NVMe, dual 25 Gbps OSD Nodes 10 12 OSDs per node, 256 GB RAM, dual 25 Gbps Storage NVMe for RocksDB/WAL, SAS HDDs for main storage

Power and Cooling Considerations

Ensuring adequate power and cooling is vital for hardware longevity and reliability.

Power Recommendations:

• Use dual redundant power supplies for all nodes.
• Rack-mounted power distribution units (PDUs) offer better management and monitoring.

Cooling Tips:

• Ensure proper airflow and use temperature monitoring systems.
• Place high-density servers in well-ventilated areas.