9 Hardware

Apt can allocate experiments on any one of several federated clusters.

9.1 Apt Cluster

This is the cluster that is currently used by default for all experiments on Apt.

The main Apt cluster is housed in the University of Utah’s Downtown Data Center in Salt Lake City, Utah. It contains two classes of nodes:

All nodes are connected to three networks with one interface each:

• A 1 Gbps Ethernet “control network”—this network is used for remote access, experiment management, etc., and is connected to the public Internet. When you log in to nodes in your experiment using ssh, this is the network you are using. You should not use this network as part of the experiments you run in Apt.

• A “flexible fabric” that can run up to 56 Gbps and runs either FDR Infiniband or Ethernet. This fabric uses NICs and switches with Mellanox’s VPI technology. This means that we can, on demand, configure each port to be either FDR Inifiniband or 40 Gbps (or even non-standard 56 Gbps) Ethernet. This fabric consists of seven edge switches (Mellanox SX6036G) with 28 connected nodes each. There are two core switches (also SX6036G), and each edge switch connects to both cores with a 3.5:1 blocking factor. This fabric is ideal if you need very low latency, Infiniband, or a few, high-bandwidth Ethernet links.

• A 10 Gbps Ethernet “commodity fabric”. One the r320 nodes, a port on the Mellanox NIC (permanently set to Ethernet mode) is used to connect to this fabric; on the c6220 nodes, a dedicated Intel 10 Gbps NIC is used. This fabric is built from two Dell Z9000 switches, each of which has 96 nodes connected to it. It is idea for creating large LANs: each of the two switches has full bisection bandwidth for its 96 ports, and there is a 3.5:1 blocking factor between the two switches.

There is no remote dataset capability at the Apt cluster.

9.2 CloudLab Utah

This cluster is part of CloudLab, but is also available to Apt users.

The CloudLab cluster at the University of Utah is being built in partnership with HP and Dell. It currently consists of 4 Intel Ice Lake servers, 208 AMD EPYC Rome servers (two generations), 170 Intel Xeon E5 servers, 270 Xeon-D servers, and 270 64-bit ARM servers for a total of 9,336 cores. The cluster is housed in the University of Utah’s Downtown Data Center in Salt Lake City.

For the m400 and m510 node types, there are 45 nodes in a chassis with a total of seven chassis. Each chassis has two 45XGc switches; each node is connected to both switches. One switch is used for control traffic, connecting to the Internet, etc. The other is used to build experiment topologies, and should be used for most experimental purposes. Each chassis switch has four 40Gbps uplinks, the control net switch uplinks with a single 40Gb connection while the experiment net has three 40Gb uplinks.

Upon request and with help from Apt staff, users can allocate an entire chassis. When allocated in this mode, it is possible to have complete administrator control over the experiment switch in addition to the nodes.

In phase two we added 50 Apollo R2200 chassis each with four HPE ProLiant XL170r server modules. Each server has 10 cores for a total of 2000 cores.

Each server is connected via a 10Gbps control link (Dell switches) and a 25Gbps experimental link to Mellanox 2410 switches in groups of 40 servers. Each of the five groups’ experimental switches are connected to a Mellanox 2700 spine switch at 5x100Gbps. That switch in turn interconnects with the rest of the Utah CloudLab cluster via 6x40Gbps uplinks to the HP FlexFabric 12910 switch.

A unique feature of the phase two nodes is the addition of eight ONIE bootable "user allocatable" switches that can run a variety of Open Network OSes: six Dell S4048-ONs and two Mellanox MSN2410-BB2Fs. These switches and all 200 nodes are connected to two NetScout 3903 layer-1 switches, allowing flexible combinations of nodes and switches in an experiment. Note that links through the NetScout switches are only 10Gb, not 25Gb.

For phase two we also added 28 Dell AMD EPYC-based servers with dual 100Gb Ethernet ports.

Each server is connected via a 25Gbps control link (Dell S5224F switch), 2 x 100Gbs experiment links (Dell Z9264F-ON switch), and a 25Gbps experiment link (Dell S5248F-ON switch). The experiment switches are connected to the "phase two" Mellanox 2700 spine switch at 4x100Gbps (Z9264F) and 2x100Gbps (S5248F).

In the initial installment of phase three (2021) we added 180 more AMD EPYC Rome servers in two configurations.

The "-25g" variant nodes have 2 x 25Gb experiment links (Dell S5296F switches) and SATA-based SSDs, and are intended for general experimentation.

The "-100g" variant nodes have one 25Gb (Dell S5296) and one 100Gb (Dell Z9264) experiment link as well as two large NVMe-based SSDs and more cores, and are intended for network and storage intensive experimentation.

Each server is also connected via a 25Gbps control link (Dell S5296F switch).

The experiment switches are interconnected via a single Dell Z9332 using 4-8 100Gb links each.

In the second installment of phase three (early 2022), we added a small set of "expandable" nodes, 2U boxes with multiple PCIe slots available for add in devices such as GPUs, FPGA, or other accelerator cards.

Each server is also connected via a 25Gbps control link (Dell S5296F switch) and three 25Gbps experiment links (via another Dell S5296F switch).

These machines have four available full-length double-wide PCIe v4 x16 slots and 2400W power supplies capable of handling four enterprise GPUs or other accelerator cards.

They also have a 400GB Optane write-intensive SSD providing another level of storage hierarchy for experimentation.

The Utah Cloudlab cluster includes a storage server for remote datasets. The server currently has 80TB available for allocation.

Phase four (early 2025) focuses primarily on adding large scale 100Gb connectivity and more expandable nodes with an emphasis on Intel processors.

The 100Gb nodes are chassis-based Dell C6620 nodes: