Vertica Data Loss When Node Goes Down

Products

• CA Performance Management
• Network Observability

Issue/Introduction

Is there data loss when a Vertica node in a three node cluster goes down?

Environment

DX NetOps Performance Management

Resolution

If a single node in a three node cluster goes down then the load is shared between the nodes that are up, including the workload for the failed node.  Therefore there is a slight performance degradation but no data loss.  Note the K-Safety must be 1 or higher for Vertica to accomplish fault tolerance and avoid data loss.  If the K-Safety=0 then data loss is expected (Vertica will shutdown). The values are 0, 1 (3 nodes) or 2 (5 nodes).  

To determine the K-safety state of a running database, execute the following SQL command on Vertica node:

=> SELECT current_fault_tolerance FROM system;

current_fault_tolerance ---------------- 1

(1 row)

 

Additional Information

If Vertica was setup from start as a three node Vertica cluster then the K-Safety should be 1.  However if Vertica was installed as a single Vertica nodes and later decide to included two additional nodes to form a three node cluster then the K-Safety is likely to be 0.  If this applies to you then please open a support case with Broadcom support.