Conditions for single node cluster

  • 20 March 2021
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  • raaji Nutanix Employee
  • Nutanix Employee
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A single-node cluster is configured like a regular (three-node or more) cluster in many ways, but here are some of the conditions. Nutanix offers the option of a single-node cluster for ROBO implementations and other situations that require a lower cost option and accept lowered resiliency protections.

  • Single-node clusters are supported only on a selected set of hardware models.

Refer the following article for details 

single-node-supported-hardwares

  • Do not exceed a maximum of 1000 IOPS

  • Do not exceed a maximum of 5 guest VMs . To protect the guest VMs from a scenario of node failure, nutanix recommends to configure backups.

  • These are unlike single-node replication targets which are for replication and backup purposes.

  • LCM is supported for software updates, but not firmware updates. 

  • There is no built-in resiliency for Prism Central on a single-node cluster. Do not create a Prism Central instance (VM) in the single node cluster.

  • Async DR is supported for 6 hour RPO only

  • Use external DNS and NTP servers. It is recommended to put DNS and NTP servers on a different cluster.

  • All user VMs must be shut down before upgrading a single-node cluster. A warning box appears if any guest VMs are running.

  • Single node clusters enter read-only mode when certain requirements are not 

  • met or a disk fails. An alert (a yellow exclamation mark) is generated in the web-console that the single-node cluster has entered read-only mode.

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Disk Failure can be categorized as 2 types

  1. SSD Failure 

  • If the SSD fails, the cluster goes into read-only state. In the read-only state, there are no create, read, update or delete operations and no cluster changes

  • If the SSD is unresponsive then data loss is at risk. To mitigate this, make sure there are more than 1 SSD in the cluster

  1. HDD Failure

  • The HDD failure is handled in the same way as that of a normal cluster and none of the situations that occur when the SSD fails occur in the case of HDD

  • If there is insufficient rebuild capacity when an HDD is unresponsive, then the cluster can fill up and IO can fail.

Raaji
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