An instance is a virtual machine launched in the public Cloud or in a Virtual Private Cloud (VPC), composed of compute, storage and memory elements, which runs an Operating System (OS) and can host any of your business applications. You can choose between different hardware configurations called instance types, and between different machine images to serve as a template for the instances to be launched.

The following topics are discussed: 

General Information About Instances

An instance is the exact equivalent of a physical machine, virtualized and launched in the Cloud using an Outscale machine image (OMI) as a template and an instance type as hardware configuration. An OMI provides at least an OS and possibly other software applications. For more information, see About OMIs.

Instances are composed of virtualized cores (vCores), memory and storage. This storage is composed of permanent Block Storage Unit (BSU) volumes : the root device of the instance is a BSU volume used to store all the OS files and other data if needed. You can launch instances using an OMI composed of several volumes, or attach additional volumes to this instance at any time. For more information, see Block Storage Unit (BSU).

3DS OUTSCALE provides three categories of instance types, between which you can choose depending on your needs in terms of compute and memory performance:

  • Custom instances, for which you can define the amount of vCores and memory you want
  • 3DS OUTSCALE-specific predefined instances, for dedicated purposes (for example, Big Data or high performance computing), with a predefined amount of vCores and memory
  • AWS-compatible predefined instances

You can modify the instance type after launch . For more information, see Modifying an Instance Attribute.


Instances can be either in the public Cloud or in a VPC. By default, an instance is launched in the public Cloud and the subnet ID is set to None on Cockpit. You can also place an instance in the Availability Zone (AZ) of your choice, within the Region of your account. If you do not specify any AZ, the AZ A is used by default.

Instances are assigned a private IP address at launch. If you launch instances in the public Cloud, they also receive a public IP address, unless you specified the private-only tag in the user data. This public IP address can be replaced by an External IP address that can be fixed to the instance. EIPs can also be used to add a public IP address to an instance in a VPC. For more information, see About EIPs.
You can add additional IP addresses to instances in a VPC through network interfaces. For more information, see About FNIs.
For more information, see About Instance Lifecycle > Launch. For the list of available public IP ranges, see 3DS OUTSCALE Public IP Addresses.

You can launch multiple instances with the same attributes at the same time. Therefore, several instances can have the same name. The Count attribute enables you to define a minimum and a maximum number of instances to launch. If the maximum number of instances cannot be launched because of insufficient capacity, the highest possible number of instances above the specified minimum count are launched. If the minimum number of instances you specified cannot be launched because of insufficient capacity, no instances are launched at all.

Each launch request creates a reservation that contains all the instances launched in the request, identified with a reservation ID. Each instance of a same reservation receives an ami-launch-index that you can use to apply some parameters to specific instances within the reservation. The first launched instance is numbered zero (0), the second is numbered one (1), and so on.


To identify your resources more easily, you can add tags to them. For more information, see Tagging Your Resources.

When launching an instance, you need to specify a keypair to use to connect to this instance. For more information about keypairs, see About Keypairs.



Instance Attributes

When launching an instance, you need to select several defining attributes. These attributes can be modified afterward. For more information, see Modifying an Instance Attribute.

An instance has the following attributes:

  • Block device mappings which define volume attachments and whether the volumes are deleted when the instance is terminated. For more information, see Defining Block Device Mappings.
  • An instance type, which determines compute, memory and storage capabilities. For more information, see Instance Types.
  • The possibility to disable termination to prevent accidental termination of the instance.
  • A keypair, which is a pair of SSH keys (public and private) with which you can connect to the instance. For more information, see About Keypairs.
  • Security groups, which enable you to manage traffic to and from the instance. For more information, see About Security Groups.
  • A shutdown behavior, which determines whether the instance stops, terminates or restarts when you initiate its shutdown.
  • Whether source-destination check is enabled for the instance. For more information, see Tutorial: Setting Up a NAT Instance.
  • User data, which enable further fine-tuning of your instance. For more information, see Configuring an Instance with User Data and 3DS OUTSCALE Tags.



Instances and Security Groups

Every instance must be launched behind a security group. Security groups act as a network virtual appliance for switching and firewalling, and therefore allow or deny traffic for one or more instances. For more information, see About Security Groups.

By default, a security group does not allow any inbound flow to your instances. You must specify the rules for this security group depending on your needs and your architecture. You can add or remove security group rules at any time, but you cannot associate an existing instance with another security group once launched.

A Default security group is available for your account. This security group only enables interactions between instances using this same security group. You can however modify its rules if needed.

In the public Cloud, security groups only filter inbound flows. In a VPC, security groups filter both inbound and outbound flows.

A security group rule is composed of the following elements:

  • Flow: Inbound or outbound.
  • Protocol: TCP, UDP or ICMP.
  • From port: The beginning port.
  • To port: The ending port.
  • Source CIDR: The CIDR network address to filter on.
  • Source security group: Another security group to filter on.



Instance Tenancy and Dedicated Instances

By default, instances are placed on servers shared by other 3DS OUTSCALE accounts. However, you can specify that you want to place your instances on dedicated servers at launch. For more information, see the instance tenancy in Creating / Launching Instances.

Dedicated instances do not share allocated hardware with other accounts, but only share it with non-dedicated instances belonging to the same account.

Using dedicated instances enables you to benefit of the full capacity of the server. The following tenancy options are available:

  • default: Your instance is placed on a shared allocated hardware.
  • dedicated: Your instance is placed on a dedicated allocated hardware.

You need to specify the instance tenancy at launch. You cannot set an instance as dedicated after launch. For more information, see Creating / Launching Instances.

When using a Virtual Private Cloud (VPC), you can set the tenancy option for the whole VPC when creating it. If you set the VPC tenancy to default, you have to set the tenancy attribute to dedicated for each instance you want to be on a dedicated server. If you set the VPC tenancy to dedicated, the tenancy attribute of instances launched in the VPC is automatically set to dedicated. You cannot modify the tenancy option of your VPC once created.


Reserved Instances

Reserved instances are instances you can reserve in a specified Availability Zone (AZ) and for a specified duration. This enables you to benefit from a discounted price, while avoiding any insufficient capacity in the AZ.

For more information about reserved instances, contact our Sales department at sales@outscale.com.




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