The type of image that may be used to boot or load a device follows the same logic as images used to provision new devices. Virtual Server Instance (VSI) may utilize both Standard and Flex Images for either the boot or load process. Loading a Bare Metal Server from an image is limited to using a Flex Image.
In limited cases a virtual server might need to be migrated to a different host. If a migration is required, the virtual server is shut down, migrated, and then restarted. A virtual server might be migrated in the following cases:
- A hypervisor needs to be updated, a host is being decommissioned, or a host is not allowed to take on new instances. If a host is marked for any of these changes, when one of its virtual server is rebooted from the Customer Portal, the reboot automatically triggers the virtual server to be migrated to a different host.
- Infrastructure maintenance. You might receive an email indicating that maintenance is required on a system that is hosting your virtual server. Your virtual server might need to be migrated as part of the infrastructure maintenance.
- An upgrade to an existing instance. For consistent performance, if you upgrade an instance it might be migrated to a different host to ensure that it receives the appropriate dedicated CPU and memory.
During a maintenance window you might see a Migrate Host option display in the Actions menu of your device in the Customer Portal. Migrate Host allows you to migrate the virtual server to a new host at your convenience during a specified maintenance period. If you do not initiate the migration during the maintenance period, then the virtual server is automatically migrated to complete the required maintenance. The Migrate Host option does not persist and is only available during maintenance periods that are communicated through maintenance notifications.
You might also see the Migrate Host option if one of your virtual servers is required to have a certain level of hypervisor that is not available on the current host.
With security groups, you can enact a set of IP filter rules that define how to handle incoming and outgoing traffic to both the public and private interfaces of a virtual server instance. A security group creates a sort of virtual firewall.
For more information about the security groups feature, see Getting started with security groups in Bluemix Docs.