# Resize

Resize (or Server resize) is the ability to change the flavor of a server, thus allowing it to upscale or downscale according to user needs. For this feature to work properly, you might need to configure some underlying virt layers.

This document describes how to configure hosts for standard resize. For information on cross-cell resize, refer to Cross-cell resize.

## Virt drivers

Todo

This section needs to be updated for other virt drivers, shared storage considerations, etc.

### KVM

Resize on KVM is implemented currently by transferring the images between compute nodes over ssh. For KVM you need hostnames to resolve properly and passwordless ssh access between your compute hosts. Direct access from one compute host to another is needed to copy the VM file across.

Cloud end users can find out how to resize a server by reading Resize an instance.

## Automatic confirm

There is a periodic task configured by configuration option `resize_confirm_window` (in seconds). If this value is not 0, the `nova-compute` service will check whether servers are in a resized state longer than the value of `resize_confirm_window` and if so will automatically confirm the resize of the servers.

this page last updated: 2026-08-20 01:33:50

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