VM Storage Settings for Migration, Resize, or EvacuationΒΆ

The migration, resize, or evacuation behavior for an instance depends on the type of Ephemeral storage used.

Note

Live migration behavior can also be affected by flavor extra specifications, image metadata, or instance metadata.

The following table summarizes the boot and local storage configurations needed to support various behaviors.

Instance Boot Type and Ephemeral and Swap Disks from flavor

Local Storage Backing

Live Migration with Block Migration

Live Migration w/o Block Migration

Cold Migration

Local Disk Resize

Evacuation

From Cinder Volume (no local disks)

N/A

N

Y

Y

N/A

Y

From Cinder Volume (w/ remote Ephemeral and/or Swap)

N/A

N

Y

Y

N/A

Y

From Cinder Volume (w/ local Ephemeral and/or Swap)

CoW

Y

Y (CLI only)

Y

Y

Y

Ephemeral/Swap data loss

From Glance Image (all flavor disks are local)

CoW

Y

Y (CLI Only)

Y

Y

Y

Local disk data loss

From Glance Image (all flavor disks are local + attached Cinder Volumes)

CoW

Y

Y (CLI only)

Y

Y

Y

Local disk data loss

In addition to the behavior summarized in the table, system-initiated cold migrate (e.g. when locking a host) and evacuate restrictions may be applied if a VM with a large root disk size exists on the host. For a Local CoW Image Backed (local_image) storage type, the VIM can cold migrate or evacuate VMs with disk sizes up to 60 GB

Note

The criteria for live migration are independent of disk size.

Note

The Local Storage Backing is a consideration only for instances that use local Ephemeral or swap disks.

The boot configuration for an instance is determined by the Instance Boot Source selected at launch.