It is a single node.
the output of 'openssl s_client':
CONNECTED(00000003)
---
Certificate chain
0 s:CN = sh01.pm.dvision.org
i:C = US, O = Let's Encrypt, CN = Let's Encrypt Authority X3
1 s:C = US, O = Let's Encrypt, CN = Let's Encrypt Authority X3
i:O = Digital Signature Trust Co...