The design goals of a Telecom-inspired Edge Server are to not only to complement existing installations such as traditional Baseband Units (BBUs) all the way out to the cell site, but to eventually replace the purpose-built proprietary platforms with a cloud-based and open solution.  The new Dell Technologies PowerEdge XR8000 achieves this goal, in terms of form factor, operations, and environmental specifications.

Figure 1. XR8000 2U Chassis

The XR8000 is composed of a 2U, short depth, 400mm class Chassis with options to choose from 1U or 2U half-width hot-swappable Compute Sleds with up to 4 nodes per chassis.  The XR8000 supports 3 sled configurations designed for flexible deployments.  These can be 4 x 1U sleds, 2 x 1U and 1 x 2U sleds or 2 x 2U sleds.

The Chassis also supports 2 PSU slots that can accommodate up to 5 power capacities, with both 120/240 AC and -48 VDC input powers supported.

The 1U and 2U Compute Sleds are based on Intel’s 4^th Generation Xeon Scalable Processors, up to 32 cores, with support for both Sapphire Rapids SP and Edge Enhanced (EE) Intel® vRAN Boost processors.  Both sled types have 8 x RDIMM slots and support for 2 x M.2 NVMe boot devices with optional RAID1 support, 2 optional 25GbE LAN-on-Motherboard (LoM) ports and 8 Dry Contact Sensors though an RJ-45 connector. 

The 1U Compute Sleds adds support for one x16 FHHL (Full Height Half Length) Slot (PCIeFigure 2. XR8610t 1U Compute Sled Gen4 or Gen5).

The 2U Compute Sled builds upon the foundation of the 1U Sled and adds support for an additional two x16 FHHL slots.

These 2 Sled configurations can create both dense compute and dense I/O configurations.  The 2U Sled also provides the ability to accommodate GPU-optimized workloads.

This sledded architecture is designed for deployment into traditional Edge and Cell Site Environments, complementing or replacing current hardware and allowing for the reuse of existing infrastructure.  Design features that make this platform ideal for Edge deployments include:Figure 3. XR8620t 2U Compute Sled

• Improved Thermal Performance
• Efficient maintenance operations
• Reduced power cabling
• Simplified generational upgrades

Let’s take a look at each one of these.

Improved thermal performance

The XR8000 is designed for NEBS Level 3 compliance, which specifies an operational temperature range of -5^oC to +55^oC.  However, creating a server that operates efficiently through this whole temperature range can require some “padding” on either side.  Dell has designed the XR8000 to operate at both below -5^oC and above +55^oC.  This creates a server that operates comfortably and efficiently in the NEBS Level 3 range.

On the low side of the temperature scale, as discussed in the sixth blog in this series, commercial-grade components are typically not specified to operate below 0°C.   New to Dell PowerEdge design, is the XR8000 sled pre-heater controller, which on cold start where the temperature is below -5°C, will internally warm the server up to the specified starting temperature before applying power to the rest of the server.

On the high side of the temperature scale, Dell is introducing new, advanced heat sink technologies to allow for extended operations above +55°C. Another advantage of this new class of heat sinks will be in power savings, as at more nominal operating temperatures the sled’s cooling fans will not have to spin at as high a rate to dissipate the equivalent amount of heat, consuming fewer watts per fan.

Efficient maintenance operations

Figure 4. XR8000 Front View.   All Front MaintenanceFigure 5. XR8000 Rear View.  Nothing to see here.

In many Cell Site deployments, access to the back of the server is not possible without pulling the entire server.  This is typical, for example, in dedicated Site Support Cabinets, with no rear access, or in Concrete Huts where racks of equipment are located close to the wall, allowing no rear aisle for maintenance.   

Maintenance procedures at a Cell Site are intended to be fast and simple.  The area where a Cell Site Enclosure sits is not a controlled environment.  Sometimes, there will be a roof over the enclosure to reduce solar load, but more times than not it’s exposed to everything Mother Nature has to offer.  So the FRU (Field Replaceable Unit) maintenance needs to be simple, fast, and quickly bring the system back into full service.  For the XR8000, the 2 basic FRUs are the Compute Sled and the PSUs.  Simple and fast not only restore service more quickly, but the shorter maintenance cycle allows more sites to be serviced by the same technicians, saving both time and money.

Reduced power cabling

Up to four compute sleds are supported in the XR8000 Chassis, supplied by two 60mm PSUs.  If you looked at a traditional, rackmount server equivalent there would be either 4U of single socket or 2U-4U of dual-socket servers.  Assuming redundant PSUs for each server, there would be between four to eight PSUs for equivalent compute capacity and between four to eight more power cables.   This consolidation of PSUs and cables not only reduces the cost of the installation, due to fewer PSUs but also reduces the cabling, clutter, and Power Distribution Unit (PDU) ports used in the installation.

Simplified generational upgrades

With the release of Intel’s new 4^th Generation Xeon Scalable Processor, a server in 2023 can execute the equivalent of multiple servers from only 10 years ago.  It can be expected that not only will processors efficiently continue to improve, but greater capabilities and performance in peripherals, including GPUs, DPU/IPUs, and Application Specific Accelerators will continue this processing densification trend.  The XR8000 Chassis is designed to accommodate multiple generations of future Compute Sleds, enabling fast and efficient upgrades while keeping any service disruptions to a minimum.

Conclusion

It is said that imitation is the sincerest form of flattery.  In this respect, our customers have requested, and Dell has delivered the XR8000, which is designed in a compact and efficient form factor with similar maintenance procedures as found in the existing, deployed RAN infrastructure.

Building upon a Classical BBU architecture, the XR8000 adopts an all-front maintenance approach with 1U and 2U Sledded design that makes server/PSU installation and upgrades quick and efficient.