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.