Within the context of the Mayastor application, a "Mayastor Node" is a Kubernetes worker node on which is scheduled an instance of a Mayastor data plane pod, so is thus capable of hosting a Storage Pool and exporting Persistent Volumes(PV). A MSN makes use of block storage device(s) attached to it to contribute storage capacity to its pool(s), which supply backing storage for the Persistent Volumes provisioned on the parent cluster by Mayastor.
Kubernetes worker nodes are not required to be MSNs in order to be able to mount Mayastor-provisioned Persistent Volumes for the application pods scheduled on them. New MSN nodes can be provisioned within the cluster at any time after the initial deployment, as aggregate demands for capacity, performance and availability levels increase.
2MiB-sized Huge Pages must be supported and enabled on a MSN. A minimum number of 1024 such pages (i.e. 2GiB total) must be available on each node, which should be verified thus:
grep HugePages /proc/meminfoAnonHugePages: 0 kBShmemHugePages: 0 kBHugePages_Total: 1024HugePages_Free: 671HugePages_Rsvd: 0HugePages_Surp: 0
If fewer than 1024 pages are available then the page count should be reconfigured as required, accounting for any other workloads which may be co-resident on the worker node and which also require them. For example:
echo 1024 | sudo tee /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
This change should also be made persistent across reboots by adding the required value to the file
/etc/sysctl.conf like so:
echo vm.nr_hugepages = 1024 | sudo tee -a /etc/sysctl.conf
All worker nodes in the cluster which are intended to operate as MSNs should be labelled with the OpenEBS engine type "mayastor". This label is used as a selector by the Mayastor Daemonset, which will be deployed during the next stage of the installation. Here we demonstrate the correct labeling of a worker node named "node1":
kubectl label node node1 openebs.io/engine=mayastor