Admin Servers

Introduction

Each correlator has two administrative servers, server-1 and server-2. The servers are used to administer the correlator and take no direct part in the actual correlations. The servers provide network services like DNS, DHCP, logging, etc. They also serve up the system images for the diskless correlator hosts (e.g., swc-001) as well as provide access to the difx software installation (provided via NFS mount).

The primary server is server-1 and server-2 is maintained as a warm backup.

Naming in this document

The servers are named server-1 and server-2 on both clusters. However, for patching and other purposes it is useful to suffix those names with a "t" (test) or a "p" (production) where the actual host being referenced is clear. Thus, instructions might refer to "server-1t" for the server-1 box located on the test correlator at the AOC and server-2p to specify the secondary admin server located in DC. However, nothing on either correlator will recognize the suffix: it is intended only for documetation purposes.

Network Access

The servers utilize both of the 1G Ethernet ports provided by the hardware; one is used by the admin network and the other is used for external access.

Because the servers are administrative devices, they use the admin network (10.1.36) but do not use the high speed networks (10.1.37 and 10.1.38). All hosts and devices (e.g., PDUs, switches, environment monitor, KVMs, etc.) are accessible via the admin network.

In addition to the admin network the two servers have a second network connection outside the correlator network. At the AOC that connection is directly to the NRAO network. At the DC site, a connection is made to the USNO network and hence on to a VPN connection back to the NRAO. The externally connected NICs on the servers appear to be on a USNO-local network (192.168.24.*); switching voodoo provided by the USNO(?) allows Internet accessible IPs to be routed directly to these NICs.

Hardware

The servers are Dell PowerEdge R440 systems. They utilize Intel Xeon Silver 4114 CPUs which operate at 2.2 GHz and provide 10 cores (the CPUs are configured to disable hyperthreading). Sixteen (16) GB of RAM are available on the hosts. The servers have two 1 TB disks. The systems performs UEFI boot from a partition on one of the hard drives. The bulk of the storage on the two drives is combined into a RAID 1 partitions mounted as / (64 GB) and /export (814 GB). A number of other small partitions are also present on the disk but are not RAIDed. See the section on disk layout for more information.

-- JimJacobs - 2020-01-21