TL;DR: LRDIMM supports higher memory capacity with lower electrical load but higher cost and latency; RDIMM offers faster speeds at lower capacities with broader compatibility.
In server memory, LRDIMM (Load-Reduced DIMM) and RDIMM (Registered DIMM) primarily differ in how they manage electrical load, impacting capacity, performance, and cost. Understanding the difference between LRDIMM and RDIMM is crucial for server administrators, data center engineers, and SMB IT buyers to select the best memory for their workloads.
What is RDIMM?
RDIMM (Registered DIMM) uses a register to buffer address and command signals, improving signal integrity and allowing servers to support higher memory capacities than UDIMM. It is cost-effective, offers faster speeds at lower capacities, and is widely compatible with server platforms while supporting error correction for stability.
What is LRDIMM?
LRDIMM (Load-Reduced DIMM) uses an additional buffer to consolidate electrical loads from memory ranks into a single load, reducing strain on the memory controller and allowing for much higher capacities per DIMM. LRDIMMs are ideal for high-capacity, high-throughput environments like HPC, large-scale virtualization, and big data analytics.
LRDIMM vs RDIMM: Key Differences
- Buffering: RDIMM uses a register; LRDIMM uses an advanced memory buffer to reduce electrical load.
- Capacity: LRDIMM supports the highest capacities, up to 8 ranks per DIMM; RDIMM supports high but lower capacities than LRDIMM.
- Performance: RDIMM offers faster speeds and lower latency at lower capacities; LRDIMM enables higher throughput in high-load scenarios.
- Power Consumption: LRDIMM consumes more power due to additional buffering.
- Cost: RDIMM is more economical; LRDIMM is more expensive due to advanced technology.
- Compatibility: LRDIMM requires platform support and should not be mixed with RDIMM or UDIMM.
Comparison Table: RDIMM vs LRDIMM vs MCR DIMM
| Feature | RDIMM | LRDIMM | MCR DIMM |
| Buffering | Register | Memory Buffer | Advanced Buffer with Multi-Rank Design |
| Capacity | High | Highest | High |
| Performance | Fast at lower capacities | High throughput at high capacities | Very high bandwidth for DDR5 servers |
| Latency | Lower | Higher base, lower under load | Low latency with high bandwidth |
| Power Consumption | Moderate | Higher | Higher (DDR5 power management) |
| Cost | Lower | Higher | Higher |
| Use Cases | General server workloads | HPC, virtualization, large databases | High-performance DDR5 servers |
| Mixing | Cannot mix with LRDIMM | Cannot mix with RDIMM | Not mixable with DDR4 RDIMM/LRDIMM |
When to Use RDIMM?
Use RDIMM when your workloads require up to 32GB DIMMs, prioritizing cost-efficiency and fast speeds for general-purpose server applications with ECC stability.
When to Use LRDIMM?
Choose LRDIMM for high-capacity workloads requiring DIMMs larger than 32GB, supporting large-scale virtualization, HPC, and data analytics environments that need maximum capacity and bandwidth.
When to Use MCR DIMM?
MCR DIMM (Multi-Component Rank DIMM) is a DDR5 memory technology designed for servers requiring the highest bandwidth and lowest latency, ideal for next-generation HPC and data-intensive environments on supported platforms.
Frequently Asked Questions (FAQ)
Q1: What is the main difference between LRDIMM and RDIMM memory?
LRDIMM uses memory buffers to reduce electrical load and support higher capacities, while RDIMM uses a register to buffer signals, providing faster speeds at lower capacities and lower cost.
Q2: Should I choose LRDIMM or RDIMM?
Choose LRDIMM for memory-intensive workloads requiring large DIMMs (>32GB). Choose RDIMM for general workloads using DIMMs up to 32GB for better cost and speed.
Q3: Can LRDIMM memory be mixed with RDIMM memory?
No, mixing LRDIMM with RDIMM is not recommended as it can cause compatibility issues or system instability.
Q4: What is a RDIMM memory?
RDIMM, or Registered DIMM, is server memory with a register that buffers signals to improve stability, allowing higher capacities and supporting ECC for error correction.
Q5: What is the difference between MCR DIMM and RDIMM?
MCR DIMM is a DDR5 server memory with advanced buffering for higher bandwidth and lower latency, while RDIMM uses a register to improve signal integrity and is commonly used for DDR4/DDR5 servers with lower bandwidth requirements.
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