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Install Caching Nodes

Caching nodes are simplyblock storage containers that are co-located with the workloads on Kubernetes workers. They utilize directly attached NVMe disks on the worker nodes to provide an ultra-low latency write-through cache for disaggregated or hybrid simplyblock clusters.

Prerequisites

Service Direction Source / Target Network Port(s) Protocol(s)
ICMP ingress control - ICMP
Cluster Control ingress control 5000 TCP
spdk-http-proxy ingress storage, control 8080 TCP
SSH ingress storage, control, admin 22 TCP
Docker Daemon Remote Access ingress storage, control 2375 TCP
FoundationDB egress storage 4500 TCP
Docker Daemon Remote Access egress storage, control 2375 TCP
Docker Swarm Remote Access egress storage, control 2377 TCP
Docker Overlay Network egress storage, control 4789 UDP
Docker Network Discovery egress storage, control 7946 TCP / UDP
Graylog egress control 12202 TCP

Caching nodes, like storage nodes, require huge page memory to hold the internal state. Huge pages should be 2MiB in size and a minimum of 4096 huge pages should be allocated at boot time of the operating system.

demo@worker-1 ~> sudo sysctl -w vm.nr_hugepages=4096

Info

To see how huge pages can be pre-reserved at boot time, see the node sizing documentation section on
Huge Pages.

demo@worker-1 ~> sudo systemctl restart kubelet

demo@worker-1 ~> kubectl describe node worker-1.kubernetes-cluster.local | grep hugepages-2Mi

demo@demo ~> kubectl describe node worker-1.kubernetes-cluster.local | grep hugepages-2Mi
  hugepages-2Mi:      9440Mi
  hugepages-2Mi:      9440Mi
  hugepages-2Mi      0 (0%)    0 (0%)

demo@worker-1 ~> sudo yum install -y nvme-cli
demo@worker-1 ~> sudo modprobe nvme-tcp
demo@worker-1 ~> sudo modprobe nbd

demo@demo ~> kubectl label nodes worker-1.kubernetes-cluster.local type=simplyblock-cache

Afterward, the worker node can be described to check that the node-selector type is successfully set.

Example output of a successfully configured worker node
demo@demo ~> kubectl describe node worker-1.kubernetes-cluster.local | grep simplyblock-cache
                    type=simplyblock-cache
Example Caching Node-enabled StorageClass
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: encrypted-volumes
provisioner: csi.simplyblock.io
parameters:
  type: cache
  ... other parameters
reclaimPolicy: Delete
volumeBindingMode: Immediate
allowVolumeExpansion: true