# Watcher Overload standard deviation algorithm

We find it necessary to check load of hosts in a cluster using overload algorithm that based on standard deviation. It is implemented as watcher's strategy. 2 properties might be checked:

CPU

RAM

The standard deviation strategy checks these properties of compute nodes every minute:

Computes the ratio between occupied resourses and total resourses for each compute node

Computes arithmetic mean of each property for all compute nodes

Calculates standard deviation of each property

Checks if any properties exceed the acceptable standard deviation and if they do, makes decision to migrate

The goal of this algorithm is minimizing the standard deviation.

## Blueprint information

- Status:
- Complete

- Approver:
- Antoine Cabot

- Priority:
- Medium

- Drafter:
- Alexander Chadin

- Direction:
- Approved

- Assignee:
- Alexander Chadin

- Definition:
- Approved

- Series goal:
- Accepted for newton

- Implementation:
- Implemented

- Milestone target:
- newton-1

- Started by
- Alexander Chadin on 2016-04-18

- Completed by
- Antoine Cabot on 2016-05-30

### Related branches

### Related bugs

### Sprints

### Whiteboard

Alex, any update on specs ?

Sorry for waiting, we have been too busy. We have been working on it since this January.

Gerrit topic: https:/

Addressed by: https:/

Add Overload standard deviation strategy spec

Addressed by: https:/

Add Overload standard deviation strategy